Proving a negative is technical term in logic.  It refers to attempting to prove (for example) that there are no human beings who have ever existed who are 20 feet tall.  It is logically impossible to prove that.  Or proving that there are no extra-terrestrial beings on earth.  Those statements cannot be proven.  So generally, logicians would say that the only proof would be to prove that there is a human 20 ft tall, or that there is an extra-terrestrial being by producing one.  As a logical exercise, please prove that Mickey Mouse doesn't exist as a sentient being.  

The math equation you produced is not a negative by the definition commonly accepted for proving a negative.  

I have produced reasons to believe but not proof.  You on the other hand have produced no reason to believe that ICE could enforce local laws.  I cannot prove a negative.  But you have not even attempted to give a reason to believe that ICE agents could enforce local laws.