The Oregon Senate delivered a powerful message in support of tightening regulation on medical marijuana Wednesday by voting 29-1 for a bill aimed at curbing diversions to the black market.

Although the measure has drawn intense opposition among many patients and growers, lawmakers said that the success of the state's new recreational pot market depends on getting a tighter handle on marijuana ostensibly grown for patients.

Sen. Ginny Burdick, D-Portland and chair of a House-Senate committee on implementing the marijuana legalization initiative passed by voters in November, said the large amount of marijuana diverted to the black market makes it harder for legal sellers to compete and could even threaten federal action against the state.

The state now produces an estimated $1 billion a year of "largely black market medical marijuana that ends up all over the country," said Burdick, calling it a "problem which is far worse than I ever dreamed."

Senate Bill 964 limits the number of plants allowed on medical marijuana farms and requires regular reporting by growers on what they are growing and distributing. Urban residential growers would be limited to 12 plants while those outside those zones would be limited to 48 plants. Existing growers could have twice as many plants, but only to serve their existing customer base.

The strong Senate vote for the bill also made clear how senators felt about an issue that had hung up the House-Senate marijuana committee - the question of how much power cities and counties would have to ban medical marijuana dispensaries.

Senate members of the committee insisted that city councils and county commissions should have the ability to prohibit them, subject to voters gathering the signatures necessary to hold a referendum. House members argued that only voters should be allowed to implement a ban.

That issue will have to be resolved after SB 964 goes over to the House, where it is expected to be sent to the Joint Ways and Means Committee. But Burdick said the strong vote could help persuade House members to go along.

Sen. Floyd Prozanski, D-Eugene, cast the only vote against the measure, saying he didn't think the League of Oregon Cities was negotiating fairly on the issue. He said the league put out a booklet in March giving cities a variety of methods for banning medical marijuana dispensaries.

--Jeff Mapes

503-221-8209

@Jeffmapes