Practically speaking, you can't check every business; it's like taxes, some people will cheat. Yet if you demonstrate that the costs of getting caught are high enough, you can deter significant violations.
The real question now, however, is if this action was merely a show put on by the administration to show they are thinking about practical measures? It was the largest such raid in history, certain to generate lots of favorable press; but will anything follow in its wake?
Will the Republicans really take on business interests on this issue?