One day last April, I followed a 25-year Telluride local as he slid up to a boundary rope at the top of the resort’s Revelation Bowl, glanced over his shoulder to see if anybody was watching, and ducked out of bounds. We traversed the rim of the ­famous Bear Creek drainage, a shimmering, 3,000-plus-acre playground of 45-degree couloirs and untracked powder ringed by the high, jagged peaks of Colorado’s San Juan Mountains. A dozen other skiers were visible up the valley.

My guide—who asked not to be named, for fear of losing his job and his ski pass—picked a line, and we plunged downward, carving into creamy spring snow. Five months ­earlier, this terrain wouldn’t have been off-limits, but in December 2010 the U.S. Forest Service—leaseholder of Telluride’s more than 2,000 acres—had forced the resort to close the gates into Bear Creek, shutting down some of the best lift-accessed backcountry skiing in North America. At issue is a 30-acre bacon strip of land that separates Bear Creek from the town of Telluride, 2,850 feet below.

The controversial real estate speculator Tom Chapman had bought the parcel and several others for $246,000 from a ­doctor named George Greenberg the previous spring; then he complained to the Forest Service that skiers were trespassing as they ­exited the drainage on their way back to town. Chapman says that he and his business partner, a hippie turned chef named Ron Curry, plan to erect a gold mine on the site or perhaps build a ­European-style backcountry chalet. In January 2011, Chapman also filed a lawsuit against the resort’s parent company, Telluride Ski and Golf (TSG), contending that he has the right to keep an old road to his claim open year-round—a road better known to ­Telluride skiers as See Forever, an intermediate run and one of the hill’s main thoroughfares.

Judging by a letter he wrote to the Forest Service in May 2010, soon after he closed on the claims, it appears that Chapman’s goal is t...