You need a CITES export permit from the USA and a Canadian CITES import permit (I am speaking for SPS, LR and clams). I am not sure what the rules are for softies I never looking into those
Its not impossible to get, the problem lies when you try to get aquacultured corals. Believe it or not, its actually significantly harder to get farmed corals because most of the time, the exporter (for example ORA) is not able to positively identify the mother colony on the frags you are trying to import. Without actually being able to provide proof of this, your CITES permit cannot be issued. So you actually have a far easier time getting a CITES permit for wild ocean collected corals, which makes zero sense since farmed corals are actually far more sustainable.
I looked into doing this a few years ago. The issue also lies this takes time and work from both parties (you as the importer, and the wholesaler because they also need to be willing to supply and fill out paperwork on their end).