Why is this a difficult concept?
If you let them commit crimes, they get the impression they can get away with it.
But, if you can believe it, deportation worked on the honour system, even for violent criminals. If you had been ordered deported, you were expected to be good about it and see yourself out of the country. Armed guards seldom met anyone at the prison gates and escorted them to the airport.
Jaser (who it must be remembered has not yet been convicted of planning to explode a train bridge and derail a VIA train), should have been expelled from Canada, if not after the first or second conviction, then certainly after the third.
If there really are 30 000 people in Canada with deportation orders, some of whom have criminal convictions to their name, maybe Sun News should bring back their most wanted list so that we can track them down. There are probably a handful of would-be jihadis among them.