Supporters of a saner marijuana policy scored a small victory this week when the Obama administration said it would authorize more institutions to grow marijuana for medical research. But the government passed up an opportunity to make a more significant change.

The Drug Enforcement Administration on Thursday turned down two petitions — one from the governors of Rhode Island and Washington and the other from a resident of New Mexico — requesting that marijuana be removed from Schedule 1 of the Controlled Substances Act. Drugs on that list, which include heroin and LSD, are deemed to have no medical use; possession is illegal under federal law, and researchers have to jump through many hoops to obtain permission to study them and obtain samples to study. Having marijuana on that list is deeply misguided since many scientists and President Obama have said that it is no more dangerous than alcohol.

Over the years, Congress and attorneys general have deferred to the expertise of the D.E.A., which is the part of the Justice Department that enforces the nation’s drug laws. So the D.E.A. has amassed extensive control over drug policy making. It determines who gets to grow marijuana for research and which scholars are allowed to study it, for example. It has strongly resisted efforts by scientists, state officials and federal lawmakers to reclassify marijuana by rejecting or refusing to acknowledge evidence that marijuana is not nearly as harmful as federal law treats it.

Since 1968, the University of Mississippi has been the only institution allowed to grow the plant for research. This has severely limited availability. The D.E.A. now says that because researchers are increasingly interested in studying marijuana, it will permit more universities to grow the cannabis plant and supply it to researchers who have been approved to conduct studies on it. This should make it easier for researchers to obtain varieties of marijuana with varying concentrations of different compounds.