Selectmen this week are expected to approve a motion that would ask Town Meeting voters in May to adopt an 18-month moratorium on allowing town land or structures to be used as medical marijuana treatment centers. The Zoning Board of Appeals had already submitted a zoning bylaw to Town Meeting that would allow the board to issue special permits for medical marijuana treatment and dispensing facilities and cultivation. Selectmen chairman John Stagnone said the town can go the moratorium route by replacing the zoning article that the board has already approved for the warrant, either by holding a special Town Meeting within the annual Town Meeting or providing Town Meeting with a substitute motion. Stagnone said he expects to take the matter up at the meeting Tuesday and expects to use the substitute motion. “I think going with the moratorium is right for Stoughton,” said Stagnone. “This will allow us more time to review the state regulations [still being written] and review our current zoning and see how this can fit into one of our existing zoning districts or whether we will create a new district.” The moratorium being considered is based on one passed by Burlington and recently approved by the state attorney general’s office. Stoughton voters overwhelmingly approved a ballot question last fall approving medical marijuana.