WASHINGTON — The Obama administration on Monday told federal authorities not to arrest or… WASHINGTON — The Obama administration on Monday told federal authorities not to arrest or prosecute medical marijuana users and suppliers, paving the way for some states to move forward with plans to create officially sanctioned dispensaries to provide the drug as relief for a series of maladies.

The move by the Justice Department ended months of uncertainty over how far the Obama White House planned to go in reversing the Bush administration’s federal stance on the controversial issue, which held that authorities should continue to enforce federal drug laws even in states with medical marijuana laws on the books.

In new guidelines circulated Monday, the Justice Department told prosecutors and federal drug agents that they have more important things to do than to arrest people as long as they are obeying the laws of states that allow some use or sale of medical marijuana.

The move clarifies what some critics had said was an ambiguous position of the Obama administration, especially in the battleground state of California, where authorities raided numerous clinics and made arrests over the years. Some of those California raids followed Obama’s inauguration in January, after, as a presidential candidate, he had pledged to stop them.

The American Civil Liberties Union and other advocacy groups welcomed the move as an important step toward a comprehensive national policy on medical marijuana because they will allow states to implement their own laws without fear of interference from the federal government.

In all, 13 states have some form of medical marijuana laws. But some, like New Mexico, Rhode Island and Michigan, have been reluctant to implement programs due to fears that they would be struck down by courts, or shut down by authorities, said Graham Boyd, director of the ACLU’s California-based Drug Law Reform Project.

“They can now move forward and set up distribution networks in states that are officially sanctioned to do so, and this will also shift the public view, sending a signal that this is something that accepted” by the federal government, Boyd said.

Boyd said he also hoped the new policy will spur local governments within California and other states with well-established medical marijuana programs to weed out fly-by-night dispensaries that are in it for the huge potential profits that can be made. Currently, he said, there are few rules in California regarding how to screen for legitimate patients, what kinds of quantities of marijuana are appropriate and how much profit can be made.

“The big news outside of California is that this will get the states off the dime and in California, clarify the line between what is legal and illegal, and reduce some of the chaos that exists and that’s a good thing,” Boyd said.

Attorney General Eric H. Holder Jr. said the new guidelines were adopted, in part, because federal law enforcement agencies have limited resources and need them for more pressing priorities. One of those priorities is countering the spread of violent Mexican drug cartels, which use the vast profits from their marijuana sales in the United States to support other criminal activities, the guidelines say.

The Justice Department will continue to prosecute people whose claims of compliance with state and local law conceal operations that are “inconsistent” with the terms, conditions or purposes of those laws, according to Holder and Deputy Attorney General David W. Ogden, who issued a three-page memorandum outlining the new guidelines.

The change in policy was criticized by many law enforcement advocates, and some conservative groups and members of Congress.

“By directing federal law enforcement officers to ignore federal drug laws, the administration is tacitly condoning the use of marijuana in the U.S.,” said Rep. Lamar Smith, R-Texas, ranking member of the House Judiciary Committee. He said the decision undermines the administration’s get-tough plan to attack the Mexican drug cartels, which he said are growing marijuana in U.S. national parks and fueling drug-related violence along the U.S.-Mexico border.

Other states that allow some use of marijuana for medical purposes are Alaska, Colorado, Hawaii, Maine, Michigan, Montana, Nevada, New Mexico, Oregon, Rhode Island, Vermont and Washington.

But California is unusual in its allowance of dispensaries that sell marijuana and advertise their services. The post-inauguration raids of such clinics in Venice, Marina del Rey, Playa del Rey and South Lake Tahoe spurred activists to demand that Obama put some kind of formal policy in place.

The new guidelines stress that authorities should go after those who improperly abuse or obtain medical marijuana or use clinics as a cover for drug dealing and other illegal activity.

In particular, the memo urges authorities to pursue cases which involve violence, the illegal use of firearms, selling marijuana to minors, excessive financial gains and ties to criminal enterprises.