How do you say ILLEGAL in a language that these Invaders understand?
Most people south of the border do not understand (nor care) about rules and laws. Everything is pushed to the limit before some policeman pulls them over and demands a “mordidita” payment in the palm for their inconvenience.
Case in point... Do you think a stop sign means stop to them? No, they will casually observe and coast through. Speed limits ????? Ha.
So, when it comes to concept of what being illegal is... they don’t care. They will continue do it as long as they can get away with it...