WASHINGTON – The administration of President Donald Trump may ramp up enforcement of federal laws against recreational marijuana use, a White House spokesman said on Thursday, setting up potential conflicts in states where the drug is legal.

More than two dozen U.S. states have legalized marijuana for either medical or recreational purposes, and the administration of former President Barack Obama mostly looked the other way. But White House spokesman Sean Spicer said the Trump administration may distinguish between medical and recreational use of the drug.

Spicer's comments came on the same day that a nationwide poll from Quinnipiac University in Hamden, Connecticut, showed 71 percent of registered voters favored allowing states to decide whether marijuana should be legal.

"I do believe you'll see greater enforcement of it," Spicer said at a news conference. "Because again there's a big difference between the medical use … that's very different than the recreational use, which is something the Department of Justice will be further looking into."

Spicer's comments drew criticism from the country's nascent legalized marijuana industry as it recovers from a scare after Trump's nomination of former Alabama Sen. Jeff Sessions, a longtime anti-drug campaigner, as attorney general.

"It would be a mistake for the Department of Justice to overthrow the will of the voters and state governments," Aaron Smith, executive director of the National Cannabis Industry Association, said in a statement.

Seventy-five percent of cannabis stocks in an index followed by Arcview Market Research dropped on Thursday after Spicer's remarks, analyst Michael Arrington said in an email.

A spokesman for Sessions, who was confirmed as attorney general earlier in February, declined to comment on marijuana enforcement on Thursday.

But during his confirmation hearings, Sessions said his job was not to enforce only some laws.

Marijuana remains illegal under federal law, but it has been legalized for recreational use in eight states, including Washington, Colorado and California, as well as the District of Columbia. Last year, legal sales reached $7 billion and generated half a billion dollars in sales taxes.

Among registered voters in the Quinnipiac University survey, just 23 percent said the U.S. government should enforce federal laws against marijuana in states that have legalized it for recreational or medical use, and 71 percent said it should not.