equivocation

You used one word to mean two things and hoped nobody noticed.

Wrong: “The law says you have rights, and it’s a law of nature that the strong win.”

Right: “Those are two unrelated senses of ‘law.’”

The argument only works while the word is allowed to slide.

The argument looks valid because the same word appears throughout. It isn’t, because the word changed jobs partway through and the logic only holds for one of them.

How to answer it: define the term and make it stay defined. Most equivocations don’t survive being asked “which sense do you mean?”

Now go define your terms.