The recent Texas shooting brings up the question of how someone who has been deported multiple times from the US can legally be approved to enter again.
@Mr. Daystar any sights on US immigration law in this aspect?
For Canada, you have 3 "levels" of removal orders. The most minor (usually for first time offenders on a simple overstay) is a Departure order, which lets you apply to re-enter Canada with no waiting period, so long as you leave within 30 days of the departure order to leave the country & you report that departure with Canadian border agents.
The 2nd level is an Exclusion order which happens if you don't get your ass out of Canada within 30 days of the deportation order, or you did other bad stuff like misrepresentation of your application, etc. This gives you a 1 to 5 year ban from re-entering Canada, after which you can apply to re-enter.
The last is the Deportation order, which is basically a ban for life from entering Canada again. Stuff like serious criminality in Canada will get you this.
And of course, you have biometrics taken each time, so you can't skirt the system by changing your name or using fake documents. In the case of the Texas shooter, he would not have been approved to re-enter, and likely would have been a lifetime ban.