CONCORD, N.H. — Fulfilling a campaign promise, Gov. Maggie Hassan signed a law Tuesday making New Hampshire the 19th state to allow seriously ill residents to use marijuana to treat their illnesses.

“Allowing doctors to provide relief to patients through the use of appropriately regulated and dispensed medical marijuana is the compassionate and right policy for the state of New Hampshire, and this legislation ensures that we approach this policy in the right way with measures to prevent abuse,” Hassan said in a statement.

Additional Photos

In this August 2012 file photo, many varieties of marijuana seedlings are on display. Gov. Maggie Hassan has signed a law making New Hampshire the 19th state to allow seriously ill residents to use marijuana to treat their illnesses. John Patriquin / Staff Photographer

The law allows patients with cancer and other conditions to possess up to 2 ounces of marijuana obtained from nonprofit dispensaries. To qualify for medical marijuana, New Hampshire residents would have to have been a patient of the prescribing doctor for at least 90 days, have tried other remedies and have exhibited certain symptoms.

The law took effect with Hassan’s signature but getting the program operating could take up to two years. The bill calls for a commission to be appointed as soon as possible to implement the new system. Patients must be issued special identification cards to obtain the drug from dispensaries and possess it.

“This legislation is long overdue and comes as a relief to the many seriously ill patients throughout New Hampshire who will benefit from safe access to medical marijuana,” said Matt Simon, a New Hampshire-based legislative analyst for the Marijuana Policy Project. “Those suffering from debilitating conditions like cancer and multiple sclerosis deserve legal, safe, and reliable access to medical marijuana.”

Under the new law, up to four dispensaries can be licensed and have a maximum of 80 marijuana plants, 160 seedlings and 80 ounces of marijuana or 6 ounces per qualifying patient. They also would have a limit of three mature cannabis plants, 12 seedlings and 6 ounces for each patient who designates the dispensary as a treatment center.

The compromise bill passed last month eliminated an option for patients to also grow marijuana at home.

Home-grow option supporters had argued some patients need legal access to the drug more quickly and waiting for dispensaries to start operating put them through needless suffering, but Hassan said she wouldn’t sign the bill if it included those provisions.

“By providing strong regulatory oversight and clear dispensing guidelines, this bill addresses many of the concerns that were expressed throughout the legislative process. (The bill) legalizes the use of medical marijuana in a way that makes sense for the state of New Hampshire and gives health providers another option to help New Hampshire’s seriously ill patients,” the governor said.

Maryland also passed a law this year that allows academic medical research centers to establish programs to dispense marijuana to sick patients. The law takes effect in the fall. A medical marijuana bill also is awaiting action by the Illinois governor. The District of Columbia also allows the drug’s use for medical purposes.