As Canada has recently legalized recreational marijuana use nationally, border patrol and customs officers on either side of the border prepare for new issues. Some U.S. states have legalized marijuana to varying degrees, Canada has done so nationally, but the U.S. federal government still lists marijuana as a Schedule 1 drug under the Controlled Substances Act. Therefore, U.S. border patrol can seize, detain, and seek to prosecute any individual crossing into the U.S. with marijuana from Canada, even if it was a legal amount/format both in the country of departure and state of arrival. Thus, the various prohibitions and regulations of marijuana use will continue to frustrate unwitting travelers who may think they are comporting to the "new" laws on marijuana use and possession in their home country. You should into Canada or the U.S. with marijuana as it will likely be seized, and you may be arrested for prosecution.