Every time I read a story that talks about Trudeau's penchant for waffling and backtracking, I sincerely wish he was his father. 
Whether you liked him or not, at least Pierre Elliot Trudeau had a spine. He also had an ear for the people, and if a majority of the people of his time had favoured cannabis legalization, he would not have hesitated. Nor would he have spent his energy trying to find a way to put control of cannabis into the hands of liberal donors and profiteers. 
He would have simply said: Its time for the Government of Canada to stop interfering in how Canadians choose to relax and enjoy themselves. Then he would have invited John and Yoko over, had a Smoke In by the Rideau, and been done with it.
Pierre didn't have the public support for cannabis legalization. Justin would if he'd simply light the match.