BOISE - An American Indian tribe and environmentalists pleaded Monday with a federal judge, telling him he's the only thing standing between them and the next giant oil-field equipment shipment along a winding Idaho mountain highway toward Canada's tar sands.

Meanwhile, a lawyer for a General Electric Co. subsidiary told U.S. District Judge B. Lynn Winmill that the courts had no authority to interfere with the company's second 225-foot-long, 640,000-pound water evaporator, slated to travel on U.S. Highway 12 on Sept. 18.

Its first evaporator, shipped on the route in August, attracted numerous protesters, 20 of whom were arrested.

Winmill promised a ruling this week.

U.S. 12 is a federally designated Wild and Scenic River corridor along the Lochsa and Clearwater rivers running through the Nez Perce Tribe's reservation and U.S. Forest Service territory.

For three years, it has been ground zero in disputes between foes of big industrial shipments to the oil fields in Alberta - including the Nez Perce Tribe who says the highway isn't the appropriate route - and companies, including ExxonMobil, and now GE, who want to use the highway as the shortest, cheapest alternative.

"Unless this court acts, nobody is going to stop the next megaloads shipment in nine days," Laird Lucas, a lawyer for the shipment foes, told Winmill.

The tribe and environmentalists from Idaho Rivers United contend that allowing the next GE shipment will cause irreparable harm to the rights of the Nez Perce people and damage the corridor's environmental values. Lucas predicts additional protests, if nothing is done.

"There will be public health and safety issues," he said. "The highway will be closed down."

Though ExxonMobil resorted to other Idaho highways to get nearly all of its gear to Canada amid the protest, GE is insisting on U.S. 12, saying delays to getting its equipment to Canada on time could cost it $3.6 million in damages. Richard Boardman, a lawyer for the company's Resources Conservation Company International unit, suggested shipment foes were using the specter of further protests to pressure Winmill.

"I know this court is not going to react to that kind of mob mentality," Boardman said, arguing U.S. 12 was actually the route with the fewest impacts. "It is the most environmentally-friendly route to get this equipment to the customer," he said, prompting guffaws from a packed courtroom audience heavy with shipment foes.

Winmill warned the crowd to be quiet, otherwise he'd eject them from the courtroom.

Earlier this year, Winmill ruled the Forest Service did have the authority to intervene on whether the megaloads could legally pass through territory managed by the agency.

During Monday's hearing, however, he raised the question of whether a federal judge could go one step further in this case: to actually put a halt to shipments, when the Forest Service hadn't already done so.