The lead defendant in the case of the four men who in May illegally walked on the Grand Prismatic Spring in Yellowstone National Park may go to jail for violating a national park rule in Colorado, according to court records.

On Sept. 13, British Columbia resident Charles Gamble was charged with a misdemeanor count of flying a drone over Mesa Verde National Park, and he is scheduled for his arraignment in that case on Thursday. He has said he will plead guilty.

Thomas Fleener, the Laramie attorney who has been representing Gamble and three others with High on Life/SundayFundayz, wrote Friday that incarceration is possible in this case.

In a motion he filed with U.S. District Court in Colorado, Fleener asked the judge to allow him to withdraw as attorney because Gamble no longer wanted him and because Gamble is broke, which means he will need a federal public defender.

While jail is a theoretical punishment with this misdemeanor, a comment he made in his motion marks the first time incarceration is a real possibility.

"While the AUSA does not take a position in this motion, I am authorized to inform the Court that the United States may be seeking confinement in this case, thereby triggering the Defendant's right to counsel," Fleener wrote.

Fleener also has asked federal court in Wyoming to allow him to be dismissed in the Yellowstone National Park cases that drew international outrage.

On Tuesday, Gamble and the other defendants -- Alexey Andriyovych Lyakh and Justis Cooper Price-Brown of British Columbia, and Hamish McNab Campbell Cross of New Zealand -- are scheduled to appear in federal court in Mammoth Hot Springs to face the charges in two cases stemming from their actions on May 14.

That day, they video-recorded themselves looking at signs telling to people to stay on the boardwalk. They then recorded themselves leaving the boardwalk and walking across the sensitive bacterial mat of the Grand Prismatic Spring.

Gamble, Price-Brown, Lyakh and Cross were charged with not staying on designated boardwalks or trails, and with creating a hazardous or physically offensive condition, according to documents filed in Wyoming U.S. District Court.

That same day, they illegally photographed images in the park for commercial purposes without a permit, and were charged on Oct. 7. The misdemeanors are punishable by up to six months in jail and a $5,000 fine.

Fleener did not say whether the federal prosecutor in Wyoming may be seeking a jail sentence for the defendants.

The defendants also allegedly have violated rules about public lands at Death Valley, California, and on U.S. Bureau of Land Management land in Utah, but no federal charges have been filed there.