Senate Judiciary Chairman Patrick J. Leahy is asking the Obama administration to clarify its position on the recreational use of marijuana, which two states legalized by referendum Nov. 6 but remains illegal under federal law.

The Vermont Democrat on Thursday released a letter he sent to Office of National Drug Control Policy Director R. Gil Kerlikowske on Dec. 6 asking how the agency intends to react to new state laws in Colorado and Washington that allow adults to possess up to 1 ounce of marijuana for personal purposes. The states’ laws also allow adults to create licensing schemes for the cultivation and distribution of the drug. Marijuana remains a Schedule I controlled substance under federal law, with cultivation, possession and distribution punishable by prison time.

Leahy pressed the drug control office, which is part of the White House, on how it intends “to prioritize federal resources” in light of the new state laws and whether the administration can guarantee that it will not prosecute state officials who are involved in the licensing process.

“What assurance can and will the administration give to state officials involved in the licensing of marijuana retailers that they will not face federal criminal penalties for carrying out duties assigned to them under state law?” Leahy wrote.

Leahy also said Thursday that he will call a Judiciary Committee hearing early next year on those questions and others involving marijuana policy.

State-federal discrepancies over marijuana policy are nothing new. According to the Marijuana Policy Project, an advocacy group, 18 states and the District of Columbia now allow the use of medical marijuana, even though the federal government does not. For the most part, the Justice Department has not prosecuted violations of federal law in those states, but there have been notable exceptions in California and elsewhere.

The new laws in Colorado and Washington go significantly further than the medical marijuana measures, however, and have raised concerns among state and federal lawmakers alike over how the legal differences will play out on the ground.

State officials from Colorado and Washington have asked the administration for guidance, with the department so far saying only that its position “remains unchanged.”

A bipartisan group of House members, meanwhile, is sponsoring legislation (HR 6606) that would prevent federal law from pre-empting state marijuana laws, an approach that sponsor Diana DeGette, D-Colo., has called a simple way to keep federal laws while respecting the state measures.

In his letter Thursday, Leahy suggested that he could be open to supporting legislation like DeGette’s.

“Legislative options exist to resolve the differences between federal and state law in this area and end the uncertainty that residents of Colorado and Washington now face,” he wrote. “One option would be to amend the Federal Controlled Substances Act to allow possession of up to 1 ounce of marijuana, at least in jurisdictions where it is legal under state law.”

Melissa Attias contributed to this report.