Originally Posted by H2O_Goalie
Yes. The service provider might not like it (though there's absolutely no way for them to know), but it's perfectly legal.
ACTUALLY, the law doesn't quite agree with you there. There is such a thing as the DMCA, and it can be invoked in these matters. And then there is the operator agreement; often when you purchase a phone or signup for service you agree to certain clauses regarding unlocking.
There still is no open and shut answer for unlocking, but for the time being I'll let this disucssion stay open.