Immigration enforcement doesn't care if X-Man Northstar save American lives for a living; he's a Canadian citizen and his recent marriage to American Kyle Jinadu does nothing to change that fact. That's thanks to DOMA, which prohibits the federal government from recognizing same-sex marriages.
And as you see in the screenshot above (click to expand), those immigration officials come knocking in the latest issue of Marvel's Astonishing X-Men. Northstar happens to be out fighting villains when they call, but no doubt this fictional ICE will make another appearance in months to come. Unless our real world heroes can use their powers to finally overturn the discriminatory law, of course.