The nation’s fast-growing marijuana industry remains cautiously optimistic but uncertain about how the Trump administration will handle cannabis enforcement across the country.

Attorney General nominee Jeff Sessions, testifying at the start of his confirmation hearings on Tuesday, pointed out that marijuana remains illegal at the federal level, but that the federal government has limited enforcement resources. Eight states — Alaska, California, Colorado, Maine, Massachusetts, Nevada, Oregon and Washington — have legalized recreational marijuana, as has the District of Columbia. And 29 states permit some form of medical marijuana use.

Marijuana-industry workers worry Sessions, a Republican U.S. senator with a longstanding opposition to marijuana legalization, could crush an nascent industry that’s on track to be worth $21 billion within three years. During his testimony Tuesday, Sessions reminded Congress that it has the power to legalize pot nationally. During the election, President-elect Trump said he would respect states’ rights and leave alone...