San Diego County is just saying "no" to enforcing a California law passed last December that requires counties to give ID cards to registered patients who use medical marijuana so they won't get busted for having pot.

"To use medical marijuana cards and at the same time go after gangs and what they're doing, it's absolute hypocrisy to me," said San Diego County Supervisor Bill Horn.

Click in the video box to the right to watch a report by FOX News' Trace Gallagher.

In 1996, Californians were the first in the nation to pass an initiative legalizing marijuana for medical purposes.

"Patients ought to be able to have access to medical marijuana. Everyone agreed by vote that's what we want," said Jerry Meier, chairman of the county's Medical Marijuana/Cannabis Task Force.

Thumbing their noses at Sacramento, earlier this month county supervisors voted three to two against issuing pot ID cards. The supervisors plan to sue the state, arguing that any marijuana use violates federal law.

County attorneys have warned that litigation will be costly and likely lose in court. The supervisors' response — they're up for the challenge.

"We think the federal court has to make that decision. Who's right, who's wrong. I mean, you put us in the middle here," Horn said.

Medical marijuana advocates say the voters have spoken and counties should listen. They add that they worry innocent patients will face prosecution.

"You could have someone coming down here from up north with their card, getting pulled over by a sheriff ... and it costs you in the county thousands of dollars in a lawsuit because they weren't enforcing the state card program," Meier said.

For now the lawsuit shapes up as San Diego County versus the state of California, but legal experts say it's unlikely to remain within state borders and could wind up in federal court, another test of whether the central government or the states have the right to decide if medical marijuana is legal.