Capital City Care currently offers four strains of medical cannabis, priced from $380 to $440 an ounce. (Linda Davidson/The Washington Post)

The Justice Department issued new guidance to U.S. attorneys on the enforcement of federal marijuana laws Tuesday, ending for the most part months of speculation over what posture the feds would take toward states with looser cannabis laws.

Questions over the federal marijuana enforcement were heightened after Colorado and Washington voted last year to decriminalize small amounts of marijuana, but they had also been presented well beforehand by the medical marijuana programs established in 18 states and the District.

A read of the new guidance memorandum, from Deputy Attorney General James M. Cole, should offer some assurance to the District’s medical marijuana industry that they can do business for the time being without fear of federal agents raising their facilities.

There is a catch, the memo makes clear: Localities with legalized marijuana industries must have “strong and effective regulatory and enforcement systems to control the cultivation, distribution, sale, and possession of marijuana.”

“A system adequate to that task must not only contain robust controls and procedures on paper; it must also be effective in practice,” the memo continues. “Jurisdictions that have implemented systems that provide for regulation of marijuana activity must provide the necessary resources and demonstrate the willingness to enforce their laws and regulations in a manner that ensures they do not undermine federal enforcement priorities.”

By that standard, the District should be in good stead. The city’s medical marijuana system is among the nation’s most tightly regulated, with a strictly limited number of cultivation centers and dispensaries; tight security and handling requirements; and recommendations limited to patients certified by a doctor to be suffering from a small number of maladies.

The District’s approach has been criticized by some medical marijuana advocates for being too limited in scope — not allowing home cultivation, for instance — but D.C. Council member David A. Catania (I-At Large), one of the system’s architects, said the Justice Department memo vindicates lawmakers’ decision to devise a “responsible and structured” program.

“There are definitely reasons why we constructed the infrastructure we chose for medical marijuana,” he said.

A representative of one District medical marijuana purveyors, Capital City Care, said the new federal policy is good news for both sellers and patients. “The memo calls for strong regulations on the local level, and we feel like that’s exactly what we’ve got here,” said spokesman Scott Morgan.

That said, the memo still gives U.S. attorneys wide discretion to prosecute marijuana crimes touching on eight “enforcement priorities,” ranging from distribution to minors to the use of the legal marijuana industry as a pretext for illegal trafficking to the prevention of drugged driving and “other adverse public health consequences associated with marijuana use.”

The District’s system provides for the possible sale of medical marijuana to minors, though it is unclear whether any have actually applied for patient certification. Also what constitutes an “adverse public health consequence” is open for broad interpretation. A spokesman for U.S. Attorney Ronald C. Machen Jr. was out of the office Thursday and did not respond to an e-mail seeking more information on the office’s posture on the city medical marijuana program.

But the Cole memo indicates that as long as the District maintains its tight regulations and actually enforces them, the feds will maintain a hands-off policy: “[P]rosecutors should continue to review marijuana cases on a case-by-case basis and weigh all available information and evidence, including, but not limited to, whether the operation is demonstrably in compliance with a strong and effective state regulatory system.”

Pedro Ribeiro, a spokesman for Mayor Vincent C. Gray, said there are no plans to loosen the reins anytime soon. “The District has a very robust enforcement mechanism in place and a very robust monitoring system in place,” he said.  “We’ve got a system in place; the system is working well.”

Consider, however, that the memo is nothing more than a federal administrative policy, and with Congress unlikely to weigh in on marijuana policy anytime soon, there is no guarantee that the policy won’t change down the road.

As Catania put it, “You always worry a little about a future attorney general taking a different view.”