Cheaper Canadian Presc, DRUGS Legal? Where?

My father is in need of a rather expensive drug to treat his liver condition. His current medication bill for month's worth pill is $400!

Laterly I've been hearing lot about Canadian online prescription drug that costs only as half as much. What is legality surrounding these? Is there a loophole? Does anyone know any source?

Not trying to break the law, and I won't if it is criminal in nature, but I think drug companys make obscene profit in us market (ave. 85% profit), and I don't see a reason to pay so much here in state, where it is same drug sold in Canada or overseas. Any advise to help out my father would be really appreciated.