The walls of marijuana prohibition have crumbled all around New Hampshire. It is now legal for adults in all three neighboring states to grow and possess cannabis, and retail sales will soon become a reality in Massachusetts, Maine, and Canada. Sadly, Gov. Chris Sununu continues to oppose legalization, in part because he continues to rely on terrible advice from New Hampshire’s so-called “drug czar,” former Manchester police chief David Mara. Last week, during an appearance at Dartmouth-Hitchcock…