MARIJUANA AND BORDER CROSSING – You can be denied entry if you verbally admit being in possession of or smoked weed at any time in your life. “Canada’s Public Safety Minister Ralph Goodale has discouraged Canadians from lying to American border guards if questioned about their marijuana use, Saunders said there can be grave consequences for being truthful — including being barred entry to the U.S. for life. Not every U.S. border agent asks travellers whether someone has consumed cannabis in their lifetime — this type of question is entirely discretionary — and Canadians are not required to answer it.” Sure. Just try to assert that right.
An immigration lawyer is warning that more Canadians could be denied entry into the U.S. after weed legalization
Source: Canadians could face more scrutiny at the US Border when weed becomes legal