Medical marijuana supporters face a tough challenge this legislative session in Minnesota, where Gov. Mark Dayton says he won't sign anything without the backing of law enforcement -- and authorities say they're strongly opposed.

Proponents say medical decisions should be left to doctors, not law officers. Tom Lehman, a lobbyist for marijuana use for the chronically ill, says Minnesota's proposal would have tight restrictions.

He says advocates will try to sit down with law enforcement.

But Dennis Flaherty, executive director of the Minnesota Police and Peace Officers Association, says authorities don't support legalizing marijuana for any purpose. He says legalizing medical marijuana would conflict with federal law.

Law enforcement leaders offered no suggestions when asked if there is any provision they might approve.