There is no controlling authority. You could put 15 different provisos and nobody would get in trouble. Like this: You hire somebody at $150,000. One month later they get an evaluation and there salary is adjusted down to $75,000. Easy peasy.
We need to end family chain immigration and birth right citizenship. Do that first then debate who we still let in. We also need to hold all the sponsors accountable for those they financially guaranteed. Start by withholding their tax refunds or EITC.