Attorney General-designate, Sen. Jeff Sessions, R-Ala. testifies on Capitol Hill on Tuesday at his confirmation hearing before the Senate Judiciary Committee. (AP Photo/Alex Brandon)

In his Senate confirmation hearing on Tuesday, Sen. Jeff Sessions, President-elect Trump's nominee for attorney general, declined to say whether he'd adhere to the more lenient marijuana enforcement guidelines adopted by the Obama administration's Justice Department in states that have legalized medicinal or recreational marijuana use.

"Would you use our federal resources to investigate and prosecute sick people who are using marijuana in accordance with their state laws, even though it might violate federal laws?" Senator Patrick Leahy (D.-Vermont) asked.

"I won't commit to never enforcing federal law, Senator Leahy," Sessions replied. "I think some of [the Obama-era guidelines] are truly valuable in evaluating cases," he added. "Using good judgment about how to handle these cases will be a responsibility of mine. I know it won't be an easy decision, but I will try to do my duty in a fair and just way."

Under Obama, the Department of Justice largely adopted a hands-off approach to marijuana enforcement in states that legalized the drug for medical or recreational use, provided that certain criteria -- like keeping the drug out of the hands of children -- were met under state laws. That policy was outlined in a Justice Department document that came to be known as the Cole Memo, for former U.S. Deputy Attorney General James Cole, who drafted the memo.

Drug policy experts have said that this tacit green light from the Obama administration was instrumental in Colorado and Washington's decisions to fully follow through on recreational marijuana laws passed by voters in 2012. In November 2016, four more states including California voted to make the recreational use of marijuana legal, bringing the total to eight states plus the District. Medicinal marijuana has been legalized in 28 states.

In prior public statements, Sessions was harshly critical of the Justice Department 's approach on the issue. In an April 2016 Senate drug hearing, Sessions said, "I think one of [Obama's] great failures, it's obvious to me, is his lax treatment in comments on marijuana. It reverses 20 years almost of hostility to drugs that began really when Nancy Reagan started 'Just Say No.'"

Sessions also said at the time that "the Department of Justice needs to be clearer" on marijuana legalization and enforcement.

Sessions didn't appear to commit to providing such clarity today. He neither voiced support for the Obama-era rules, nor signaled that he was eager to throw them away altogether. Marijuana legalization advocate Tom Angell called it a "good sign that Sen. Sessions seemed open to keeping the Obama guidelines, if maybe with a little stricter enforcement of their restrictions."

"It is notable that Sen. Sessions chose not to commit to vigorously enforcing federal prohibition laws in states that have reformed their marijuana laws," said Robert Capecchi of the Marijuana Policy Project in a statement. "He was given the opportunity to take an extreme prohibitionist approach and he passed on it."

Marijuana industry leaders voiced similar notes of cautious optimism. "Though it is possible that a slightly more restrictive 'Sessions Memo' will replace the existing Cole Memo," said Frank Lane, Vice President of financial services company CannabisFN, "we do not believe an AG Sessions will disrupt the long-term growth prospects of the U.S. cannabis industry."

Later in the hearing, Sessions noted that "the U.S. Congress has made the possession of marijuana in every state, and distribution of it, an illegal act. So if that's not desired any longer, Congress should pass a law to change the rule."

Those words echo remarks by President Obama, who has repeatedly rebuffed calls to reschedule marijuana by saying that it is properly Congress' job to change the nation's drug laws.

President-elect Trump has himself given mixed signals on marijuana laws. He has spoken out about the negative effects of making marijuana recreationally available, but has said that changes to marijuana law should be handled on a state-by-state basis.

In a reminder of the low salience of marijuana reform for many lawmakers and voters, the questions to Sessions on marijuana law came roughly six hours into his first day of hearings. By that time, many of the Senators had already left the room.