Reductio ad absurdum (Latin for "reduction to the absurd"), also known as an apagogical argument, reductio ad impossibile, or proof by contradiction, is a type of logical argument where one assumes a claim for the sake of argument and derives an absurd or ridiculous outcome, and then concludes that the original claim must have been wrong as it led to an absurd result.
If John Travolta ... were to be stopped by law from purchasing
He already owns one. Legally. Argument closed.