There are no restrictions, you just need to tell your insurance its been fitted and they seem interested but don't care. They drive very different from what you'll expect and its a learning curve (short curve) . You can import from the US no issue, They need to be set up correctly so they don't push/pull your steering and track properly. The shop in Acton Ont, vintage cranks, are the provincial gurus on how they work/set up and some really good driving advice. All sidecars are not equal, personally I'd talk to them before buying anything, they are very approachable and helpful.
There is a guy in Newmarket making a beautiful car, but its about 12K all in, he builds for Indian.