PHOENIX - Gov. Jan Brewer has cleared one hurdle for new research on the possible medical benefits of marijuana.

Without comment, the governor signed legislation Tuesday to permit possession of marijuana on college and university campuses for research. The measure takes effect later this year.

The plan will most immediately help Sue Sisley, a University of Arizona physician who specializes in internal medicine and psychiatry, whose planned research project was blocked by a bill last year disallowing pot on campuses.

Gubernatorial aide Matthew Benson said his boss never intended to interfere with legitimate research when she signed the earlier bill.

The 2010 voter-approved medical marijuana law banned possession of the drug in public schools, but there was no such restriction on the use of medical marijuana on college and university campuses.

Last year, at the behest of the Board of Regents, lawmakers approved the college ban.

Proponents pointed out marijuana remains illegal under federal law. And they said the failure of campuses to have a drug-free policy endangered not only federal aid but also scholarships for students.

Sisley said she gained approval two years ago from the U.S. Food and Drug Administration to conduct a study to determine whether marijuana, in various dosages and methods of administration, can help combat veterans with post-traumatic stress syndrome.

She said her proposal had already been approved by the UA's Institutional Review Board, which must give the go-ahead for research on live subjects. The next step was to get approval from the U.S. Drug Enforcement Administration to sell her the drugs for study.

Sisley said the legislation and the governor's signature are a victory for academic research.

"It proves that science is not going to be trumped by politics," she said. And Sisley said it assures that the university system will remain "a sanctuary for research that might be considered controversial."

The bill Brewer signed leaves intact the ban on marijuana on campuses. But it creates an exception for research approved by the FDA, the DEA or the National Institutes on Drug Abuse.