I don't know all the ins and outs, but each team is allowed to have two imports unless one is a first-round pick, then they're allowed three but as soon as that first-round pick is sent back, the team has to renounce the rights to one of the other players.
That's what happened with the Mooseheads a couple years ago anyway. They had Timo Meier, so they could make two picks in the draft, took Otto Somppi and Joakim Blichfeld, but when Meier was returned, they had to renounce the rights to Blichfeld (who is now playing in Portland).
The Import Draft is two rounds and the picks rotate between each league, based on standings...not sure how they decide who gets the first pick though. If a team already has their imports, they pass on the pick. The picks were previously allowed to be traded but I think they've stopped that.
And yeah, import goalies have been banned from the CHL.