Marijuana use in the workplace has become increasingly hazy as more states legalize the drug and employers grapple with how to adjust their policies to the complex jumble of new laws and court decisions.

Two recent court cases veered from rulings that historically favored employers in states where medical marijuana is legal. Federal law still criminalizes marijuana, but 29 states have approved medical cannabis, and eight others have legalized recreational use. The clash of federal and local regulations doesn't give employers clear guidance on what actions are permissible.

Recent court rulings in Massachusetts and Rhode Island may prove instructive to employers that, while they may have power to declare a drug-free workplace, they still face liability implications under state discrimination laws. Those measures could give some protection to employees who regularly use marijuana to treat a medical condition.

“It's an evolving landscape with the development of state laws, with respect to medical and recreational use, and both types are illegal on the federal level,” said Katharine Beattie, a Mintz, Levin, Cohn, Ferris, Glovsky and Popeo member in Boston. “This area represents the intersection of the laws with respect to marijuana use and protecting employees based on disabilities.”

Related: Legal Marijuana: Budding Industry, Burning Questions

Marijuana use has spiked in the last three years in the United States, with the highest positivity rate recorded in 12 years, according to a recent analysis by Quest Diagnostics. Among illicit drugs, marijuana has increased the most dramatically. In Colorado and Washington, the rate was nearly double the national average.

Since the wave of recreational marijuana laws took off in 2014, employers generally have argued that they will follow federal law when it comes to workplace restrictions.

The Trump administration is not expected to change the federal approach to the drug. U.S. Attorney General Jeff Sessions in May urged lawmakers to roll back an amendment that prohibits the agency from using federal funds to prevent states from implementing their own state laws that authorize the use, distribution, possession or cultivation of medical marijuana.

Still, some courts and states are moving in the opposite direction from the conservative message of the Trump administration.

This month, the Massachusetts Supreme Judicial Court ruled in favor of a woman named Cristina Barbuto, who sued her former employer, Advantage Sales & Marketing LLC, for handicap discrimination after she was allegedly fired over her use of medical marijuana.

Barbuto tested positive for marijuana, which she said she uses to combat Crohn's disease. She sued the company under state discrimination laws. A judge ruled for Barbuto, rejecting the federal-law argument the company advanced.

Mintz Levin's Beattie said the Massachusetts decision was among others that open a door for employees and candidates for employment who seek accommodation for medical marijuana use under state discrimination laws.

“Employers have navigated this area to make it clear, despite laws allowing use, that use is prohibited on workplace premises on workplace hours,” Beattie said. “The decisions to date by in large have allowed employers to allow the federal prohibition to have a blanket prohibition on marijuana use in the workplace.”

The Massachusetts decision contrasts to a June 2015 Colorado court ruling that sided with the employer in a dispute over marijuana. In that case, the court found that, because marijuana is illegal under federal law, the company did not have to accommodate a cardholder's disability.

In Rhode Island, the American Civil Liberties Union sued Darlington Fabrics Co. for rescinding a paid internship offer to a woman because she was a medical marijuana card holder. Christine Callaghan, the plaintiff, had participated in the medical marijuana program for almost two years to combat frequent migraines. The company withdrew the internship offer after discovering she was a cardholder, the lawsuit alleged.

A Rhode Island Superior Court judge, ruling on May 23, said the state's medical marijuana law protects cardholders from discrimination in employment. The judge dismissed the company's claims that it did not discriminate against Callaghan.

“The only reason a given patient cardholder uses marijuana is to treat his or her disability. This policy prevents the hiring of individuals suffering disabilities best treated by medical marijuana,” the judge concluded, also acknowledging an employer still has the right to deny drug use in the workplace.

ACLU attorney Carly Iafrate said the decision could send a message to employers that people with disabilities cannot be denied equal employment opportunities because of the medication they take.

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Rulings Throw 'Everything Up in the Air'

Danielle Urban, a partner in Fisher Phillips' Denver office who advises employers on marijuana legalization, said the Rhode Island and Massachusetts rulings have created a “sea change” for how employers should think about marijuana.

“I think, in light of the recent cases, employers are saying, 'Holy cow, we thought we were OK in other states.' This throws everything up in the air,” she said.

The jumble of laws can be frustrating to employers, she said.

“I have fewer and fewer employers that have no tolerance policies. At first, everyone rushed to have these policies,” Urban said. “It's a patchwork and, if you are a national employer, we have to treat it differently in every day.”

Several states offer protections for medical marijuana users, including Rhode Island, New York and Arizona. Yet these measures only provide limited protections, said Amanda Goldman, of counsel in Coats Rose's New Orleans office. An employer's obligation to accommodate these workers is distinct from state disability discrimination laws.

Before the recent cases, there were few wins for marijuana cardholders. Goldman predicted that this will likely remain the trend until federal law shifts. Still, the Massachusetts and Rhode Island cases could be a turning tide for accommodation under state law.

She said employers are struggling with the jumble of laws and vague terms.

“If you are an employer that has a safety sensitive position, there is no way that a medical marijuana cardholder will mount a defense,” Goldman said. “If you are dealing with an office position, I think there is more headway. The laws are changing and the states are mounting a defense to federal law.”