For some environmentalists, though, it all boils down to Yellowstone's legal obligation to preserve its natural resources. Mark Pearson, former conservation director for the Greater Yellowstone Coalition, is a staunch opponent of both snowmobiling and kayaking, and he doesn't see how allowing any new activity in Yellowstone will help protect wildlife.

"There's no conservation benefit," he says. "It's nice for the national parks to be this one last bastion of places where it's not a sort of anything-and-everything-goes kind of playground – which is the way a lot of our other public lands are headed."

Despite opposition within the environmental community, American Whitewater has pushed for decades to reverse the Yellowstone ban. The group's last serious attempt was in the late '90s, when it suggested that the Park Service allow kayaking on limited sections of river on a trial basis. The Park Service immediately shot the idea down.

"They've simply not been very flexible in learning about new paddling technologies, paddling skills and the impacts – or the lack of impacts – that kayakers have on the river corridor," says Johnson, an old friend of Ammons and Lesser who has himself been arrested for attempting a Black Canyon run.

"Put a permit system on it," suggests 27-year-old Ben Kinsella, a Bozeman kayaker who made a short film of his own illegal but successful Black Canyon run. "People go backcountry skiing in there all the time – they get a permit and they're good. It's not the Park Service's job to baby everyone that goes in."

Over the last decade, kayakers have continued to covertly smuggle their boats into the park while largely avoiding a public battle. But in 2009, Congress provided a new opening: It declared the Snake and Lewis rivers, which flow through the southern part of Yellowstone into Grand Teton, "wild and scenic" – a federal designation created to protect free-flowing rivers with outstanding natural, cultural and recreational values. The Snake and Lewis aren't quite the world-class whitewater of the Black Canyon, but paddlers hope they'll create the leverage needed to wedge open the door to kayaking in the park.

Wild and scenic status has worked in kayakers' favor before. In Yosemite, the Merced River's designation compelled park officials to consider easing restrictions on boating there earlier this year. And in 2006, American Whitewater sued the U.S. Forest Service to reverse its ban on kayaking on the Chattooga River, which flows through Georgia and South Carolina. The ban was enacted in 1976 to protect trout habitat, but American Whitewater argued that it lacked justification and violated the Wild and Scenic Rivers Act. In 2007, a U.S. District Court agreed, opening the Chattooga to its first legal descent in 30 years. The decision has since been appealed, but Colburn believes it provides a legal precedent that ought to compel officials in Yellowstone to reconsider kayaking on the Snake and Lewis rivers.

"(Kayaking) provides people a really beautiful, powerful way of connecting with rivers and with nature and with the landscape," he says. "The experiences people would have are exactly the kinds of experiences that the National Park Service and the Wild and Scenic Rivers Act were set up to promote."

But the agency's first draft of a new river management plan for the Snake and Lewis, released in May, includes no plans to study the impact of opening new stretches of water to paddling. The possibility of kayaking, pack-rafting, canoeing or otherwise floating the off-limit portions of the rivers is listed under the heading "Considered but dismissed from detailed evaluation."

Unfazed, Colburn has solicited comments from American Whitewater's 5,500 members and submitted a 23-page response that he hopes will convince the agency to do a substantive evaluation. The next draft of the management plan could surface by the end of the year. But after working unsuccessfully for three years to get kayaking considered in the current draft, few boaters are holding their breath.

In the meantime, kayakers who want to tackle the Black Canyon will have to face more than just steep boulder gardens. Kayaking on closed waters in Yellowstone National Park remains a class B misdemeanor carrying a maximum penalty of six months in jail, a $5,000 fine and five years of unsupervised parole – and that's not all. "We usually request a five-year ban (from Yellowstone) for the individual," says Deputy Ranger Nick Herring. "The ban is probably more important than the fine."

For Rob Lesser, who received the relative slap on the wrist of a $25 fine for his 1986 escapade, today's punishment has reached the point of absurdity. A kayak is "a hollowed log," he says. "That's all it is. It's so simple. (This is) about access to wild places."

Editor's note: Our Nov. 11 story “Forbidden Waters” has been changed to reflect the following corrections. The original story stated that Yellowstone and Grand Teton National Parks have “blanket bans” on kayaking, but the bans are by no means comprehensive: There's a calm three-mile channel of the Lewis River in Yellowstone that's legal to paddle, and a much longer section of the Snake River in Grand Teton. The story also misstated that Mark Pearson is the conservation program director of the Greater Yellowstone Coalition. Pearson is the former director; Scott Christensen is the current director. Further, the organization American Whitewater has 5,500 members, not 4,500; and the story incorrectly stated that in Yosemite, the Merced River’s Wild and Scenic designation compelled park officials to ease restrictions on boating. Officials in Yosemite are currently considering easing restrictions. We regret the errors.