John H. O'Brien, a state police lieutenant who was named director of the New Jersey medical marijuana program more than three years ago, has resigned.

O'Brien retired and his family is relocating, said Donna Leusner, a spokeswoman for the state Department of Health, in response to an e-mail asking for information on O'Brien's April 4 resignation.

In a statement, O'Brien, 54, who was with the state police for 26 years, said he was "grateful for the opportunity to be a part of one of the more significant social changes in recent history."

James Baracia, who has been with the marijuana program for more than two years, was named acting director. A supervisor who developed the criteria for inspecting the dispensaries, Baracia was a 19-year veteran of the state police who had "extensive experience with incident command and emergency first response," Leusner said.

Health Commissioner Mary E. O'Dowd said in a statement Tuesday that O'Brien was "a transformational leader" who "built a strong program with integrity that serves 4,000 patients and caregivers, and has the capacity to serve more as the program grows. He was an extraordinary advocate for patients, and worked with law enforcement to instill confidence in the communities that have hosted Alternative Treatment Centers."

Ken Wolski, executive director of the Coalition for Medical Marijuana-New Jersey, said his organization initially opposed the appointment of a law enforcement official as the head of the program, preferring a doctor or medical professional. Wolski said it soon became apparent that O'Brien was "a good guy and wanted to do the best for the patients."

Wolski said patients found O'Brien approachable, but discovered he was "frustrated in bringing about a more meaningful implementation of the medical marijuana program by the political will to prevent that from happening." Wolski said Gov. Christie's administration created delays and obstacles that hurt the program after he said at several town-hall meetings that he was concerned that medical marijuana could fall into the wrong hands and that he would oppose any expansion of the program.

Michael Weisser, chief executive of the Garden State dispensary in Woodbridge, said in a March 10 article in the Newark Star-Ledger that when he complained that the edible marijuana program was stagnating, O'Brien told him it was "out of his hands - it has to go to the eighth floor," the location of O'Dowd's office.

Later that day, Weisser said Health Department officials had preliminarily approved manufacturing plans to produce marijuana tinctures, capsules, and lozenges.

O'Dowd said in her statement that under O'Brien's tenure, three dispensaries opened and a fourth was issued a permit to cultivate marijuana.