Sixteen years after Californians approved medical marijuana, the state’s highest court is poised to decide whether cities and counties can ban cannabis dispensaries.

The long-awaited ruling by the California Supreme Court, which hears arguments on the issue Feb. 5, follows years of contradictory decisions by the lower courts operating in a void because the state Legislature has yet to define the law or pass detailed regulations.

If the court upholds bans passed by more than 200 local governments, as some legal analysts expect, more such measures are likely to be adopted.

The court also could clarify other parts of the state’s medical marijuana law, though no one expects its pronouncement to end the confusion.

“This is a subject matter that requires detailed regulations, and the California Legislature hasn’t done the job,” said Alex Kreit, a law professor who has advised San Diego on medical marijuana law.

Kreit pointed out that Colorado implemented its medical marijuana law with hundreds of regulations in a “fairly smooth process.” California legislators have yet to adopt requirements for state licensing and labeling of marijuana, among other issues.

That has left judges struggling to interpret the law and local governments uncertain of how to enforce it. Prosecutors also have been vexed. Atty. Gen. Kamala D. Harris sent letters to legislative leaders in 2011 pleading for action.

“For some reason, the perception in Sacramento has been that this will go away, that this is radioactive, so there has been a lack of leadership and commitment on the issue,” said Assemblyman Tom Ammiano (D-San Francisco), who last year introduced a bill to regulate medical marijuana. “That is changing.”

While such cities as San Francisco and Oakland moved quickly to regulate medical marijuana, others, such as Los Angeles, failed to act immediately and were inundated with dispensaries, Kreit said. Once in place, the medical marijuana providers sued cities that tried to regulate them.

“Every dot of an ‘i’ and every cross of a ‘t’ is litigated here in Los Angeles,” said Los Angeles Special Assistant City Atty. Jane Usher. “Nothing has gone unchallenged. Any time you try to regulate, hold on to your hat because you will spend the next two or three years in litigation — which makes a ban look really appealing.”

The California Supreme Court, in a handful of medical marijuana decisions, has generally interpreted the law narrowly, in one case upholding the right of employers to fire workers who use marijuana with a doctor’s recommendation, even without evidence of impaired performance.

The Legislature’s limited guidance consists of a law passed in 2003 — seven years after Proposition 215 legalized marijuana for medical purposes — that established identification cards for medical marijuana users. A subsequent law passed in 2010 banned dispensaries near schools and said cities and counties could otherwise regulate their location, operation and establishment.

Advocates of medical cannabis insist that regulating does not mean banning. They point out that the written intent of the state law was to provide uniformity among counties and make medical marijuana available to patients.

Cities and counties counter that the language of the law implies a ban is permissible. They also argue that the state Constitution gives them the right to decide local land use matters and contend that federal law, which makes marijuana illegal, preempts state law.

Former California Supreme Court Justice Carlos R. Moreno, who participated in the medical marijuana rulings, said he believes the court is likely to uphold bans in “appropriate” circumstances.

Kreit, who directs the Center for Law and Social Justice at the Thomas Jefferson School of Law, agreed that the medical marijuana advocates face the higher hurdle. Although the issue has divided the courts of appeal, more rulings than not have upheld bans.

“If they are allowed to ban dispensaries, there will be thousands of medical marijuana patients who will be out of luck and will have to turn to the black market,” said Joe Elford, chief legal counsel for a medical marijuana advocacy organization.

The state high court’s decision on bans is not likely to end the litigation. The law requires medical marijuana suppliers to operate not for profit, and Kreit foresees future litigation over what that means.

An appeals court ruled in December that dispensaries are not illegal just because they are large and have many customers, a finding that contradicted the contentions of federal prosecutors trying to close a major dispensary in Oakland.

But the appeals court also said the dispensary’s owner might be violating the law if prosecutors can show he was operating for a profit.

Ammiano said his proposed regulations, based on those suggested by Gov. Jerry Brown when he was attorney general, would provide tight regulation and taxation of dispensaries. He said he is hopeful, but not certain, that he can win passage this year.

In the meantime, advocates are considering going back to voters. Many anticipate that Californians will be asked to legalize marijuana on the 2014 ballot.

Under the current law, “it is chaos,” Ammiano said. “What we want to do is provide some order.”

maura.dolan@latimes.com