It's the "catch-22" that has plagued medical marijuana advocates and patients for decades. Lawmakers and health regulators demand clinical studies on the safety and efficacy of medical cannabis, but the federal agency in charge of such research bars these investigations from ever taking place.

But it took until now for the federal government to finally admit it.

A spokesperson for the U.S. National Institute on Drug Abuse (NIDA) told The New York Times last week that the agency does "not fund research focused on the potential medical benefits of marijuana."

Why is this admission so significant? Here's why.

Under federal law, NIDA (along with the U.S. Drug Enforcement Administration) must approve all clinical and preclinical research involving marijuana. NIDA strictly controls which investigators are allowed access to the federal government's lone research supply of pot - which is authorized via a NIDA contract and cultivated and stored at the University of Mississippi.

In short, no NIDA approval = no marijuana = no scientific studies. And that is, and always has been, the problem.

But to the folks over at NIDA, there's no problem at all.

Speaking to The New York Times in a January 19, 2010 article entitled, "Researchers Find Medical Study of Marijuana Discouraged," NIDA spokeswoman Shirley Simson said: "As the National Institute on Drug Abuse, our focus is primarily on the negative consequences of marijuana use. We generally do not fund research focused on the potential beneficial medical effects of marijuana."

Since NIDA presently oversees an estimated 85 percent of the world's research on controlled substances, the agency's ban on medical marijuana research isn't just limited to the United States' borders; it extends throughout the planet.

Previous legal attempts to break NIDA's bureaucratic logjam have failed to weaken the agency's iron grip.

In 2007, U.S. DEA Administrative Law Judge Mary Ellen Bittner ruled that NIDA's monopolization of marijuana research is not "in the public interest," and ordered the federal government to allow private manufacturers to produce the drug for research purposes. But in January of last year, DEA Deputy Administrator Michele Leonhart set aside Judge Bittner's ruling -- stating that NIDA possesses "adequate" quantities of cannabis to meet the needs of clinical investigators, and that the agency monopoly on the distribution of marijuana for research is compliant with America's international treaty obligations. (Notably, on January 26, 2010 President Barack Obama selected Leonhart to be the DEA's full time Director.)

Most recently, in November 2009 the American Medical Association's (AMA) Council on Science and Public Health declared, "Results of short term controlled trials indicate that smoked cannabis reduces neuropathic pain, improves appetite and caloric intake especially in patients with reduced muscle mass, and may relieve spasticity and pain in patients with multiple sclerosis."

However, the Council lamented that despite these encouraging preliminary results, "[T]here is a contrast between the relatively small number of patients who have been studied over the past 30 years in controlled clinical trials involving smoked cannabis and survey data from patients with chronic pain, multiple sclerosis, and amyotrophic lateral sclerosis that indicates a significant use of cannabis for self management."

And just what is the precise reason for this "contrast?" The AMA failed to specify, but to anyone who has followed this issue, the answer is painfully obvious.

Nevertheless, the AMA still resolved, "[The] AMA urges that marijuana's status as a federal Schedule I controlled substance be reviewed with the goal of facilitating the conduct of clinical research and development of cannabinoid-based medicines."

But since any future clinical trials would still require NIDA approval -- approval that the agency admits won't be coming any time soon -- it remains unclear what effect, if any, the AMA's declaration will have on facilitating medical marijuana research. If history is any guide, it's unlikely that the AMA request -- much like the cries of tens of thousands of patients before it -- will have any effect on NIDA at all.

Paul Armentano is the deputy director of NORML (the National Organization for the Reform of Marijuana Laws), and is the co-author of the book Marijuana Is Safer: So Why Are We Driving People to Drink? (2009, Chelsea Green). He may be contacted at: paul@norml.org.