AT SOME POINT nearly every new mountain biker makes the same sad discovery: Bicycles are banned from this country's 170,000 square miles of Wilderness. That's Wilderness with a capital W—those lands protected by the Wilderness Act of 1964. You can explore them by horseback, backcountry ski, or kayak, but not by bicycle. And with every new Wilderness designation, someone else's favorite trail gets closed to bikes forever.

Through years of misinformation, mountain bikes have gotten lumped in with ATVs, snowmobiles, and other maligned vehicles by people citing environmental concerns. But on several different metrics—erosion, runoff, soil compaction, loss of vegetation—study after study has found the trail impact of mountain bikers to be equal to or less than that caused by hikers, and far less than equestrians. A 2006 study by the National Park Service concluded that "Horse and ATV trails are significantly more degraded than hiking and biking trails...[T]he proportion of trails with severe erosion...is 24% for ATV trails, 9% for horse trails, 1.4% for hiking trails and 0.6% for bike trails."

If the goal truly is environmental protection, bike bans are off-topic. The Wilderness Act actually makes no mention of bicycles. What it does ban, explicitly, is motorized vehicles and, generally, "mechanical transport." This is the language used to keep bikes out of Wilderness areas, but such an absolutist interpretation of the word mechanical would also forbid ski bindings, snowshoes, and even rafts with oarlocks. Though currently allowed in Wilderness areas, all of these conveyances provide a mechanical advantage.

Of course, the authors of the Wilderness Act never meant to ban any of these. A 2004 review of the legislation by a staff attorney for California's Supreme Court found that "Congress did not intend for the Act to prohibit human-powered transport...Accordingly, the regulations of the Forest Service...prohibiting mountain bike use in Wilderness require reevaluation."

In fact, bikes weren't even banned until 1984, when the U.S. Forest Service refined regulations prohibiting their use. Depending on whose boundaries they overlap, Wilderness areas come under the jurisdiction of the Forest Service, National Park Service, Fish and Wildlife Service, or Bureau of Land Management. When the Forest Service moved against bikes, the other agencies followed.

The only people who had heard of mountain bikes in 1984 were the sport's pioneers and the groups with whom they were beginning to share trails. Those groups—hikers and equestrians with large, established organizations—joined forces under a banner of environmental protection and pushed for rules that closed Wilderness trails to anyone but themselves. Yes, that's really what happened.

Though the existing Wilderness ban is unjust by any practical measure, rolling it back would require a bureaucratic 180, an act of Congress, or an executive order, scenarios that the Boulder, Colorado–based International Mountain Bicycling Association (IMBA) has accepted as virtually impossible. So the sport's largest advocacy group spends its resources fighting to protect existing access in areas that could get Wilderness designations. For example, Forest Service proposals in Montana could ban bikes from any areas that might theoretically be designated as Wilderness. Cyclists in that state might soon lose portions of four national forests based on some bureaucrat thinking those areas should one day become Wilderness.

In order to avoid such blanket bans, IMBA works with environmental groups, land agencies, and legislators to create nuanced "companion designations" for new Wilderness areas. These congressional designations, like National Conservation Area, National Recreation Area, and National Protection Area, offer many of the same safeguards as Wilderness regulations but without the bike ban.

Say you want 100,000 acres set aside as Wilderness, but 3,000 of those acres contain trails where mountain bikers have been riding for decades. In the IMBA model, those 3,000 acres get some other designation that preserves both the environment and bike access. In return, the cyclists not only join their former adversaries in lobbying for the Wilderness designation but also in pushing for further protections of surrounding lands.

This isn't hypothetical. In 2009, IMBA partnered with Oregon Wild on a bill to designate 34,000 acres of National Recreation Area within a new 127,000-acre Wilderness. That's a nice save, by any measure. But such victories, however hard-won, will always feel a bit hollow as long as the Forest Service's wrongheaded bike ban remains.