COLUMBIA, Mo. - A compromise proposal to change a voter-approved marijuana possession law would prevent certain repeat drug offenders and those convicted of other crimes from taking advantage of the new law's lenient sentencing guidelines.

An ordinance passed by Columbia voters in November 2004 requires police to treat those possessing up to 35 grams, or 1 1/4 ounces, of marijuana as low-level misdemeanor offenders. Pot owners now avoid arrest and only face municipal court fines of no more than $250 - a punishment essentially equal to that associated with a speeding ticket.

A related measure that allows seriously ill patients to use medical marijuana within the city limits was approved on the same ballot by nearly 70 percent of Columbia voters.

Earlier this year, Columbia police officers started a petition drive to overturn the new drug possession law, which was approved by nearly 62 percent of city voters. In response, the law's chief supporter met quietly with the officers' representative, Boone County prosecutor Kevin Crane, to work out a deal.

Both Crane and civil rights attorney Dan Viets, who represents the Columbia Alliance for Patients and Education, have previously declined to discuss the particulars of the proposed compromise until it is formally presented to the Columbia City Council.

But a Sept. 2 letter from Viets to Mayor Darwin Hindman, obtained by The Associated Press under the state's open records law, outlines four proposed exemptions to the new law:

_ those found guilty of a felony in the preceding 10 years;

_ anyone found guilty in state court of a Class A misdemeanor, other than marijuana or drug paraphernalia possession, in the previous five years;

_ anyone found guilty in state or municipal court of misdemeanor marijuana possession two or more times within the previous five years;

_ anyone arrested on misdemeanor marijuana charges who is also held on suspicion of a felony or misdemeanor offense chargeable only under state law.

Crane said Wednesday the proposed compromise addresses the biggest concern by Columbia police: Hardened criminals will exploit a law intended to cut nonviolent, first-time offenders a break.

"It's essentially recognizing that there should not be a one-size-fits-all standard for offenders," he said. "If you have someone with a significant criminal history, they should not receive the same benefits as someone without a significant criminal history."

The proposed revision would also eliminate a reference to deferred prosecution and change a description of the police force's adherence as "the lowest priority" to "among the lower priorities."

The reference to deferred prosecution is unnecessary, said Viets, because local prosecutors have always had that authority and continue to do so.

Calling the proposal "the result of a long and painstaking process of negotiation," Viets asked Hindman to "actively discourage" any City Council members from proposing more changes.

"Any changes beyond the ones which both parties have agreed to will not be supported by either side," Viets wrote.

Council members contacted Wednesday said they want to wait until a proposal is submitted before weighing in. Viets said he expects the prepackaged compromise by the former opponents will be supported by elected leaders.

"I hope that will carry enough weight," he said.