WASHINGTON, D.C. — The District of Columbia’s long-awaited enactment of a medical marijuana law has paved the way for people who need the drug most to possess it without fear of being arrested.

The City Council’s unanimous vote on Tuesday approved amendments to the law first passed in 1998, when 69 percent of city voters advocated for a compassionate and responsible program. Under the District’s newest mandate, patients such as those with cancer and glaucoma will be able to purchase the drug from about five dispensaries that will be set up across the city. However, none of the dispensaries will be in close proximity to school zones.

“It has taken nearly 12 years, but the District will at last have a law that recognizes the mounting scientific consensus that, for many conditions, marijuana can be safe and effective medicine,” said Karen O’Keefe, director of state policies for the Marijuana Policy Project.

She added that the program would provide members of Congress who have not had up-close insight into such programs with a unique opportunity for doing so. “Once they see for themselves that these laws do nothing but provide compassionate care for seriously ill patients, hopefully they will understand the need to create a federal policy that no longer criminalizes patients in any state who could benefit from this legitimate treatment option,” O’Keefe said.

The Council took a preliminary vote on the measure on April 20. At-large Councilman David Catania, who spearheads the Council’s Committee on Health, said he had been looking forward to its passage. “It strikes a delicate balance in order to give patients diagnosed with chronic conditions access to medical benefits of marijuana while guarding against misuse of the drug,” Catania said.

Currently, 14 other states authorize the drug for medicinal purposes and 13 of those also approve home cultivation. The District’s bill contains provisions for the creation of a Medical Marijuana Advisory Committee to make a recommendation on home cultivation by Jan. 1, 2012.