Is it necessary to start the Alaskan intercoastal passage via canada?

Is it necessary to start the Alaskan intercoastal passage via canada?

Question about Cruise on Alaska's Inner Passage

The whole trip is from Vancouver, British Columbia to Juneau, Alaska, but there may be shorter variations. Norwegian and Holland America Line are the lines to take if you want to take a proper ocean liner, but American Safari Line runs cruises closer to