Updated: Dueling Judges Push Yellowstone National Park Snowmobile Limit Back to 720 Per Day

Yellowstone National Park officials seemingly got creative in deciding which judge's snowmobile ruling to follow for the coming winter. NPS photo.

In one of the most bizarre public lands dramas in recent history, Yellowstone National Park officials Monday afternoon said they would allow up to 720 snowmobiles into the park every day this winter.

That decision came as park officials, who earlier this fall had their preferred winter-use plan tossed out the window by a federal judge in Washington, D.C., viewed a ruling on another snowmobile lawsuit filed in Wyoming as providing them another window to revert to their 2004 winter rules.

Groups that have fought to see recreational snowmobiling in Yellowstone phased out in favor of more environmentally friendly snow coaches immediately criticized the park's decision, saying Superintendent Suzanne Lewis had misinterpreted U.S. District Judge Clarence Brimmer's ruling and was failing to protect Yellowstone's resources as best she could.

"We thought we had seen the limit of unprincipled leadership regarding decisions related to winter use in Yellowstone and Grand Teton, but obviously we hadn't," reacted Bill Wade, who chairs the executive council of the Coalition of National Park Service Retirees when he learned of the park's decision.

"NPS leaders had every opportunity to do what is 'right' for the resources and uphold the preferences of the American public as a result of the D.C. Court decision. Instead, they've chosen to cherry-pick some language in the Wyoming Court's decision that they've decided allows them to do exactly the contrary," added Mr. Wade. "We hope the incoming leaders of the Department of the Interior and the NPS see all this for what it is and turn this train-wreck around. The world's first national park deserves better."

At The Wilderness Society, which long has lobbied for cleaner snow coaches in the park, Kristen Brengel had two words of comment: "Pure politics."

Yellowstone officials, however, countered that they were, in effect, following the wishes of both judges as well as providing the snowmobiling public with certainty that Yellowstone would indeed be open for them beginning on December 15, the planned start of the winter season, snow-cover allowing.

Judge Brimmer's decision "provides for access for this winter that can be planned on, and that provides that information 20-some days in advance of the planned start of the winter season, as opposed to our process, which had the potential to come up with a decision perhaps the day of the planned start of the winter season," Yellowstone spokesman Al Nash said Monday evening.

"Both judges have told us to look forward and we’re now trying, we’re beginning the process to see how we can move forward and come up with a sustainable, long-term plan for winter use management of the parks,” he added.

It was back in mid-September when U.S. District Judge Emmet Sullivan rejected the park's winter-use plan, saying it flew in the face of logic, the environment, and the National Park Service's own Organic Act.

"According to NPS's own data," wrote Judge Sullivan, "the (winter-use plan) will increase air pollution, exceed the use levels recommended by NPS biologists to protect wildlife, and cause major adverse impacts to the natural soundscape in Yellowstone. Despite this, NPS found that the plan's impacts are wholly 'acceptable,' and utterly fails to explain this incongruous conclusion."

Now, Judge Sullivan often is the environment-friendly judge that environmentally inclined groups seek out. His counterpart in Wyoming, Judge Brimmer, is the one pro-industry groups seek out. And while Judge Sullivan was ruling on challenges to the park's winter-use plan, challenges that said the park should follow the science and phase-out recreational snowmobiling, Judge Brimmer was faced with a lawsuit filed by the state of Wyoming and Park County, Wyoming, that questioned Yellowstone's ability not only to reduce the daily number of snowmobiles in the park but also a requirement that snowmobilers be led by commercial guides.

Now, what's particularly interesting about this judicial Ping-Pong is that Yellowstone officials seemingly are being particularly selective in which decision to follow.

Here's the conclusion of Judge Brimmer's ruling, which is attached below:


Based upon the foregoing, and for reasons previously stated therein, IT IS HEREBY ORDERED that the D.C. District Court's invalidation of the final rule shall remain undisturbed by this Court.

that the NPS shall reinstate the 2004 temporary rule until such time as it can promulgate an acceptable rule to take its place.

In other words, Judge Brimmer acknowledges that he can't overturn Judge Sullivan's ruling regarding Yellowstone's winter-use plan. At the same time, he directs the park to follow the 2004 regulations "until such time as (Yellowstone) can promulgate an acceptable rule to take its place."

Now, Yellowstone officials have had the wheels in motion to do just that. Indeed, earlier this month the park released a winter-use plan that would allow up to 318 snowmobiles and as many as 78 snow coaches per day into Yellowstone for each of the next three winters.

This is what park officials said when they released that proposal: "Park managers believe an approach including both snowmobile and snowcoach access reduces impacts of both to acceptable levels. This environmental assessment addresses the impact concerns raised by the recent ruling of the U.S. District Court for the District of Columbia."

In Monday's release, however, Yellowstone officials took another tack, saying they were putting off implementation of their latest rule-making effort so they could better review public comment.

Ranger Nash said that while Yellowstone and Grand Teton officials were putting their EA process on the back burner, they planned to use comments from that process to help formulate a long-term winter-use plan. Whether such a plan will be in place before the winter of 2009-10 he could not say.

"Our planning goal has been to provide something that people can count on," said the park spokesman. "It's been an elusive goal in light of the continued legal challenges over the years."

As for the coming winter season, Ranger Nash added that Yellowstone officials really don't expect to see snowmobile traffic levels much beyond what they've seen the last two years, when daily averages were just under 300 snowmobiles.

When asked whether the snowmobile issue has become more rooted in politics than what's best for park resources, he offered this:

“That’s hard for me to determine. What I am confident saying is that the debate that surrounds winter-use in Yellowstone certainly seems to be focused on values, and not as often on the objective signs. And values discussions carry a great deal of investment and emotion. And we certainly see that reflected in every debate that involves this issue and these parks.

"Certainly, people’s political interests and leanings are part of their values. It’s hard to separate those for some people. And we’re caught up in that ‘value’ discussion. But we don’t operate in a vacuum. And we don’t pretend that we operate in a vacuum.”

Here's Monday's release from Yellowstone and Grand Teton:

A recent court order removes uncertainty about snowmobile and snowcoach access in Yellowstone and Grand Teton National Parks this winter.

Back in September, a federal judge in Washington, D.C., rejected the park’s latest winter use plan, thereby prohibiting snowmobile and snowcoach access without a new regulation. In response, the National Park Service (NPS) began work on a new temporary plan to guide winter use management in the parks, in an effort to get the parks open on time this winter on December 15, 2008. The preferred alternative in the temporary plan calls for limited, managed snowmobile and snowcoach access in the parks.

A related challenge to winter use management in the parks has been before the U.S. District Court in Wyoming. On November 7, 2008, that court ordered the National Park Service to reinstate a 2004 rule, which will allow snowmobile and snowcoach access in Yellowstone and Grand Teton this winter.

The NPS will publish a rule in the Federal Register to reinstate the 2004 rule in accordance with the Wyoming court’s order. The parks will operate under this reinstated rule for this winter season, providing visitors, area businesses, and park employees with a plan they can count on for this year.

The reinstated 2004 rule will also allow the NPS time to analyze public comment received on the temporary plan and its supporting proposed rule, in order to guide a long-term planning process for winter use in the parks as directed in the orders issued by both federal courts. Public comment on the temporary plan ends at midnight tonight, and at midnight November 20, on the supporting proposed rule.

Under the reinstated 2004 rule, motorized over-snow access will be allowed this winter as it has for the past four winters. Up to 720 commercially guided, Best Available Technology (BAT) snowmobiles and up to 78 snowcoaches will be allowed per day in Yellowstone National Park. Yellowstone’s East Entrance and Sylvan Pass will be open for motorized and non-motorized over-snow travel, subject to weather and safety constraints. Trail and off-road use of snowmobiles and snowcoaches has always been, and will continue to be prohibited.

The 2004 rule also addresses snowmobile access in Grand Teton and the John D. Rockefeller, Jr. Memorial Parkway, including access along Grassy Lake Road, and on Jackson Lake for licensed anglers.

During the last two winters, an average of about 296 snowmobiles a day entered Yellowstone. The park’s peak day was during last December, when 557 snowmobiles entered the park. Given the uncertainty caused by lawsuits on winter use, park managers forecast use levels for this winter to remain near these levels.

Brimmer-Snowmobiles.pdf132 KB


I figured this is what NPS would do, though I am surprised they are arrogant enough not to continue to push for adoption of the new temporary rule. It's pretty clear that this new (old) rule will be thrown out by Sullivan, and they had every chance to get the rule for lower numbers through. But, now that they say that this will be the limit for the winter, I have to think that Sullivan will throw out 720, and then NPS will be left with nothing for this winter. It will serve them right.

Perhaps, this is the last death throe of snowmobiling in Yellowstone. I guess the ball is in Sullivan's court to make a fairly quick ruling; it's almost impossible for him to imagine allowing this to stand when the rule that calls for fewer snowmobiles wasn't allowed to stand. If a winter then happens without snowmobiling in Yellowstone, will anyone be in a hurry to bring them back?

However, if Sullivan takes his time on this, then who the heck knows?

Jim Macdonald
The Magic of Yellowstone
Yellowstone Newspaper
Jim's Eclectic World

Bill Wade had this exactly right when he called the park's decision "unprincipled." It is hard to imagine that an agency charged with protecting and preserving the park areas of our nation would let such a decision by a superintendent stand, but I assume that is what will happen. As a former employee of Yellowstone, I am ashamed and outraged.

Rick Smith

While not technically "overturning" Sullivan's ruling, this is clearly a slap in the face to that decision. I just can't see that Judge Sullivan would allow this to stand, though I guess it depends on whether the original plaintiffs want to press it. They certainly should. If zero snow vehicles are allowed in Yellowstone this winter it will not be the court's fault, nor will it be the fault of the "tree huggers" (of which group I proudly include myself); the fault will lie directly in the lap of the Park Service. Hopefully this nonsense will begin coming to an end on Jan. 20th. I hold my breath and keep my fingers crossed that Mr. Obama's promise of a "bi-partisan" administration DOES NOT include Interior. I would also like to see the Lewis dictatorship come to an end.

Lewis is not the only dictator in the ranks of NPS superintendents.

It is high time that these unelected bureaucrats get brought back down to earth and stripped of their near despotic power over people's lives and the natural resources that are charged in their care. Lewis is just one of many and this case should open the eyes of all NPT readers and park supporters about the way these virtual Roman proconsuls wield vast powers while often ignoring the dictates of the public, courts and in this case their own park generated research.

The time to reform this position is long past due as the groundswell of outrage, just seething beneath the surface, is about to explode.

Fact is, there are businesses in West Yellowstone who have invested huge sums of money into their snowmobile fleets, not to mention the infrastructure to support the public who wish to enjoy the park in this manner. This should be based on sound science...the Park Service has already determined that snowmobiles can and should be permitted in Yellowstone and not be a detriment to the wildlife or environment.
A bunch of old crusty rangers who have fallen to the envirowacko crowd should not have the only say in this matter.

What the h*%# is a judge all the way back east in DC doing making this decision anyway? Shouldn't this be a LOCAL (Wyoming/Montana/Idaho) decision??

Hey Anon-----It's a park whose administrative HQ is located along the banks of the Potomac, where they come under the keen and perceptive purview of federal judges. Get used to it. Yellowstone is no more a LOCAL matter than nuclear testing was for Nevada. Wise up. The overlords in DC are in charge and that should inspire confidence in us all.

The Department of Interior has become a political stronghold and a disgrace to America.
So what are we going to do now, spend many millions to once again do a scientific study and then ignore it ?!?

I dearly hope that the President-elect has a plan to clean house in this Department before they manage to destroy all they have been entrusted to protect and save !


I'm not sure West Yellowstone would go out of business; most people using snowmobiles are doing so outside the park - or at least that's how it seems. But, if the economy of West Yellowstone really is going into the toilet if no snowmobiles are allowed in the park (and considering that most of town stays shut down even in the middle of the winter season, that seems doubtful as well), then NPS's move should not be welcome news to snowmobile enthusiasts because there's no way that Judge Sullivan will allow this to stand, which could mean zero snowmobiles instead of 318 per day and zero snowcoaches as well. I saw from a Wyoming politician in one news source some worry that that is in fact what will happen; it seems from a purely tactical standpoint, the snowmobile lobby should have hoped that the limit was set at 318 and then sued - instead of NPS going back to 720 (a number that simply will not be allowed to stand and may threaten all snowmobiling whatsoever).

Jim Macdonald
The Magic of Yellowstone
Yellowstone Newspaper
Jim's Eclectic World

Politics are at the heart of this battle and are clogging the arteries of our national parks. How much longer until we move to remove the life-threatening plaque of politics? This incident exposes the dismissive attitude some (many?) NPS managers take toward public comment and input. They pretend to care, gather comments, pay for expensive studies, and do what they wanted to do anyway in the face of evidence and public opposition. The whole system of public input is a sham.

Yellowstone does not exist to support a small number of businesses in West Yellowstone. It is a NATIONAL Park. In fact, Yellowstone is more even than that. As the world's first National Park it is, and has been, a model that kind of belongs to everyone. There are people who would enjoy hunting in the park, or ATVing. Many folks could make money off of these activities. The Park Service is not obligated to provide them. The Service IS obliged to allow enjoyment (only) in such a manner that will leave the park "unimpaired". Despite Shelly's assertion above, the fact is that the Park Service's own scientists have determined that snowmobiles ARE harmful, and that the best course of action would be to eliminate them in favor of snow coaches. They have been ignored. Anon #2: Yellowstone is not a local park, it is a NATIONAL PARK.

I am skeptical of the claim that the National Park Service could meet the "promulgate an acceptable rule" alternative in Judge Brimmer's decision any time soon. Indeed, Judge Brimmer says the same thing on Page 14 of his decision: "The Court finds it unlikely that the NPS will have the ability to promulgate and put into effect a rule for the winter season in a timely manner." Thus, Judge Brimmer's order in the conclusion was clearly intended to impose the 2004 rule for the 2008-2009 winter season. Whatever your opinion on this issue, I think it is indisputable that whatever final rule the National Park Service attempts to promulgate in accordance with Judge Sullivan's decision will certainly be immediately challenged by either the snowmobile lobby or the conservation lobby, or both.

Indeed, it is amusing to note that we are in the current situation because the last time the National Park Service attempted to promulgate this rule, *both* the snowmobile lobby and the conservation lobby immediately challenged the ruling, the former in Judge Brimmer's Wyoming Court and the latter in Judge Sullivan's DC Court. The National Park Service actually simultaneously petitioned Judge Brimmer to consolidate the cases in DC, and Judge Sullivan to consolidate the cases in Wyoming. Both judges demurred on this petition - and thus we ended up dueling court cases.

Looking at the whole picture, I don't see how anyone could reasonably argue that the National Park Service had any discretion to do anything other than implement the 2004 rule for the 2008-2009 winter season in Yellowstone. There's just no way to reasonably believe that the processes of public notice-and-comment, protest, and appeal could be played out in time for the 2008-2009 winter season. Failing that, the order of Judge Brimmer's ruling seems clear - the 2004 rule will be in effect.


But, what's puzzling was that NPS was in fact trying to implement a temporary rule of 318, which they fully intended to have published in time. They only scrapped those temporary plans when Judge Brimmer's ruling came down. Whether they would have succeeded in getting a new rule published is another issue; that they stopped trying altogether suggests they are setting themselves up for another court failure. They could have continued to try on the 318, and then reverted to the 2004 when that process failed. But, they simply stopped trying, which suggests they are accepting a rule for snowmobile use that the courts have now ruled is worse than the rule that has been rejected.

I would be very surprised in light of that not to see Sullivan grant an injunction. Tactically, what NPS is doing is very puzzling - either, they don't want snowmobiles in the park at all and have taken the bait in order to make that reality; or, they do, and are simply hoping that the current ruling is upheld.

We'll see how this plays out, but I think the odds went up much higher than I ever expected when Sullivan's ruling originally came out that we might actually not see any motorized over snow use inside the park this winter.

And, since roads will continue to be groomed, would that then mean they'd let non-motorized users on those roads (winterized bicycles and cross-country skiing?) - that's getting ahead of ourselves, I know. But, that question may soon become relevant.

Jim Macdonald
The Magic of Yellowstone
Yellowstone Newspaper
Jim's Eclectic World

The NPS (and fed govt.) works for us taxpayers, not us for them. They need to be reminded of that, and allow as much recreation opportunities as feasible in OUR parks. They are ALL our parks, not parks for just for enviros.
I don't buy all this enviro nonsense, and neither do most of the American people, proven by "carbon" initiatives failing this past election all over the country. You enviros need to get a life...obviously you have way too much time on your hands worrying about a little bit of exhaust from a few sleds.
I for one am looking forward to riding my new Arctic Cat sled into the park this winter! Why? Because it is FUN!!!!

From reading Judge Brimmer's opinion, it is clear that he was placing a higher value on providing certainty on short-term snowmobile policy to Park users and the surrounding Park communities, rather than on getting the right long-term policy in place for the immediate winter season. Furthermore, the opinion seems to be quite clear that the 2004 rule is to be implemented, and it seems to me that it would have been a major stretch for the Park Service to argue that they will not implement the 2004 rule at all, and would instead try and rush out the new Rule within the next 30 days - and somehow resolve the protests and appeals in that time as well. It seems to me that the National Park Service would be just asking for Judge Brimmer to slap them with a contempt of court ruling in that case.

And while it is possible that Judge Sullivan may vacate Judge Brimmer's order implementing the 2004 rule for the upcoming winter, it would be very unusual for a concurrent court to override an order of another. If Judge Sullivan did do so, such an issue would certainly be referred to the Court of Appeals - which of course could easily end up tying it up and delaying it even further.

About the only certainty in this process is that long-term resolution won't be occurring any time soon.

It has come to a point where common sense is no longer the rule. If we don't like a decesion, we sue. Come on folks it is time to start using some good old common sense. The parks were set aside as two folds: to enjoy and preserve not eliminate all activities in the name of nature. Stewardship means just that, oversee at all times in an active role not passive one time rule making that eliminates any and all activities. Stewardship is time consuming and not a one shot deal, so get used to doing some work and USE COMMON SENSE!!!


Like I said, I'm not surprised they re-instated the 720 rule; I'm surprised they used that as reason to stop on moving toward a temporary 318 rule. That move alone seems to violate the reasoning in the other court order, which they purportedly are also following. But, if the Sullivan order is simply on the merits of a permanent rule, and it's true that it provided no guidance on a temporary rule, then you may be right that Sullivan may not give an injunction. I guess we'll see.

Jim Macdonald
The Magic of Yellowstone
Yellowstone Newspaper
Jim's Eclectic World

"I don't buy all this enviro nonsense, and neither do most of the American people"...............Not true. Public opinion survey after survey, conducted by the Park Service themselves and through independent researchers, have shown that the majority of Americans feel that snowmobiles have no place in Yellowstone. I agree with Frank C. above. It is time to get politics out of our parks. Since the primary purpose of the Park Service is to provide enjoyment of the parks in such a manner as to leave them unimpaired for future generations, the Service should be run by conservationists not political appointees beholden to special interests. Environmentalism, despite what some would lead you to believe, is not a special interest; it is of interest to every single organism on this planet, including the Dick Chaney's and GW Bushes of the world, whether they choose to be ignorant of that fact or not.
"....it would be very unusual for a concurrent court to override an order of another....." Perhaps so, but in essence isn't that is exactly what Judge Brimmer did to Sullivan. Judge Sullivan said that the proposed number of snowmobiles to be allowed this winter was too many, unacceptable. Judge Brimmer comes back and says, "Well, I can't really overturn what Judge Sullivan ruled and allow that many sleds, so instead I am going to allow even more!" If that isn't "backdoor" overriding, I don't know what it is.

Jim -
My understanding is that the Park Service isn't stopping moving towards the 318 Rule - its just no longer scrambling to get that Rule in place before December. It was probably completely unrealistic to pull that off anyways, but I think that's what they were trying in light of not having any other options. I'm not sure if the Park Service has any legal provisions for instituting a temporary rule that couldn't be protested or appealed in the same way as a permanent rule, but even if they did, it would seem that Judge Brimmer's decision is essentially that the 2004 rule will be the temporary rule until such time as the full legal process regarding a permanent rule can be played out.

I am a frequent visitor to Yellowstone and would endorse nothing that truly threatened that ecosystem. However, this NON issue displays how far the fanatical left will go to pursue agendas that have no basis in scientific fact and challenge the outer limits of common sense. Yellowstone is 3500 square miles, roughly seven times the land area of the City of Los Angeles, California (470 square miles). The area of Yellowstone is almost exactly the same as the area of our two smallest states (Rhode Island and Delaware) combined. It is over 50 times the size of Washington, D.C. from where the learned Judge Sullivan issues his legal rulings.

Can you imagine what would happen if someone would propose a federal regulation that limited the number of motor vehicles in any of those places to 500 per day? Can you imagine the public reaction to a judge who ruled that limiting the number of motor vehicles to 500 in any of those places still created an unacceptable risk to the environment? I would suggest that if such a ruling were forthcoming, its author would be declared insane and measures commensurate with that declaration would be forthcoming.

Allowing 5,000 snowmobiles a day is not going to harm one pine needle on one tree. No animal going to be more endangered by a snow mobile that they are in the summer months when 90-year-old men drive 80 foot motorhomes around corners on Dunraven Road. (For those left-wingers without a sense of humor, this is what is known as sarcasm).

If these groups backing these insane regulations are truly environmentalists, why don't they really do something about it and figure out how to eradicate the blister rust and European beetles that are devastating the whitebark pine in the Park and surrounding areas? The answer is fairly obvious: It's a lot easier to hold up a protest sign, smoke a lot of dope, file frivilous lawsuits and get well-intentioned but blissfully ignorant people to donate unconscionable amounts to ridiculous causes so that those who are incapable of holding down real jobs can continue to live off the good intentions of the terminally ignorant rather than to solve complicated real problems in the real world. (How's that for a run-on sentence).

P.S. I have never ridden a snow mobile in my life but I can also see through these transparent tactics. These people do not understand the difference between National Parks, which were designed so that humans (even those not from the "enlightened" left) can enjoy and interact with nature and Wilderness areas (where human impact is designed to be next to zero). Their "agenda" is to first eliminate snowmobiles, then eliminate motor homes, then eliminate personal auto travel so that if we want to see Yellowstone we have to ride tour buses filled with AARP members while listening to the propaganda of the tour bus driver who was indoctrinated by the same people who endorse lawsuits of this nature.

Should that day ever come, I intend to organize the "Million Motor Home March". We'll surround Washington D.C., start up make-shift buffets (where we all can eat) and play our Lawrence Welk records over loud speakers (a certifiable form of torture) until they come to their senses and repent.

Seriously, folks, let's keep the snow-mobilers on the plowed roads. Employ enough law enforcement to keep the rednecks from harassing the bison (both mentally challenged creations of the Almighty, no doubt) and devote those millions in all of the 501(c)(3) corps to causes which really will protect and preserve the beauty and unique qualities of Yellowstone for generations to come.

That judge in DC should be the one to decide, in the interest of all the people hence the word National Park; not the locals with their own agenda!!!!

Have to agee with the last Anon poster. iI see nothing wrong with allowing recreational use of the park by snow mobilers. It seems the enviros want the parks to be not used by humans. That is not the purpose of the parks. They are to be enjoyed by Americans and Americans have different ways they like to enjoy the parks. I have never snowmobiled but I think it would be fun and a great way to see the park in the winter.

At least this year, all of this arguing about limits has turned out to be irrelevant. Snowmobile traffic is significantly down this year (to date); visitation overall is lower, but a lot of the shortfall has been made up for by vehicular traffic in the North Entrance. See http://www.jhguide.com/article.php?art_id=4251 .

Jim Macdonald
The Magic of Yellowstone
Yellowstone Newspaper
Jim's Eclectic World

The economic crisis is taking a toll on recreational travel. Over the past couple of decades most people lived it up, including purchasing and using mechanical outdoors toys (snowmobiles, all-terrain vehicles, jet skis, 4-wheel drive monster trucks, etc.). The crash of the economy is reverberating throughout our country, including the recreational industry. Perhaps people will rediscover their legs and the soul cleansing value of silence. All indications are that this is going to be a long haul before the economy bottoms out and begins to recover. Even then we may never regain the extreme heights of consumerism that characterized the past several years. And that just may not be such a bad thing.

The reality is that permits for snowmobiles pay for the park and those who maintain the parks salaries. Are the mountain bikers paying anything for stickers? Hikers paying for stickers for their hiking boots...?
I don't think so.
Snowmobiles should be allowed on public land. We as outdoor enthusiasts deserve to use the park in the winter just as we are allowed to drive into the park in the summer!
Do they limit campers or cars in the summer?

I think the reality is that the American public, through taxes, pays for the bulk of the park and those salaries. Snowmobile permits are a small, small pool of revenue in the overall picture, particularly when you factor in how much summer entrance fees generate for the park vs. winter entrance fees. Hikers and mountain bikers do pay entrance fees, too, when they come into Yellowstone.

Mountain bikes aren't allowed on the vast majority of NPS unpaved trails. The only ones I know of that do allow mountain bikes are essentially unpaved roads wide enough for motor vehicles.

I would note that backcountry users (i.e. backpackers) also pay special fees in many national parks, including use and reservation fees. Yosemite actually doesn't charge for backcountry permits if they're not reserved. At the very least, backpackers face quotas in some of the more heavily used backcountry areas.

In addition, campers are effectively limited by the number of available campsites.

It's not as if there aren't any precedents for special use (backpacking, camping, snowmobile) limits.