This week, the Tarrant County District Attorney’s office dismissed about 235 misdemeanor marijuana possession cases. It was an unusual move, and a response to changes in state law earlier this month.

Gov. Greg Abbott signed a measure on June 10 that had the effect of legalizing hemp and hemp products immediately. Industrial hemp was legalized nationwide last year, and Texas lawmakers wanted to conform the state’s law with the federal one so that Texans can get in on a booming industry in hemp products.

The complication: Legal hemp is making it more difficult to prosecute marijuana cases.

Hemp and marijuana both come from the cannabis plant, but hemp doesn’t have enough of a chemical called tetrahydrocannabinol (THC) to get you high. It’s the THC in marijuana that gets you stoned.

Before hemp was made legal earlier this month, the distinction between marijuana and hemp made little difference to law enforcement: Any cannabis product was illegal, and could land you in jail.

Under the new law, hemp is defined as containing less than .3 percent THC. That means that to prosecute a person for possessing marijuana, law enforcement has to prove that the substance in their possession isn’t, in fact, hemp.

In an advisory to prosecutors across the state, the Texas District and County Attorneys Association summed up the challenge presented by the new hemp-legal law: proof of THC concentration “can come only from a laboratory capable of determining that type of potency—a category which apparently excludes most, if not all, of the crime labs in Texas right now."

The Texas District and County Attorneys Association says it could take up to a year before county crime labs are equipped and ready to do the tests.

In Tarrant County, the onus is now on police departments to get a pot-like substance tested before sending a new marijuana case to District Attorney Sharen Wilson. It'll likely affect a lot of police work being in Tarrant County: Last year, 12 percent of the nearly 50,000 cases prosecuted by Wilson's office were for people caught with four ounces or less of marijuana.

The office dropped all of the misdemeanor pot possession cases that were filed after the new law went into effect, “in an abundance of caution,” says Dawn Boswell, who heads the conviction integrity unit at the Tarrant County District Attorney’s office. It’s up to prosecutors to enforce the law, she says, even when the law changes.

“Now, anything filed after June 10th has to have some proof of the concentration of the THC in the marijuana that is seized,” Boswell says.

Boswell says that the charges could be re-filed if police departments get a lab to prove the pot is pot, and not hemp. But she knows of only a a few labs capable of testing THC concentration in Texas, so it's not clear how likely it is that the cases will be re-filed.

The new pot-hemp distinction in the law means bringing even low-level pot cases will be more expensive and time consuming for both police and prosecutors, Boswell says. And because the new law went into effect immediately, prosecutors didn’t have any lead time to get everyone on the same page.

“It kind of sent everybody in the state scrambling to figure out what to do,” she said.