What is Logical but Not Legal?

A young Law student, having failed his Law exam, goes up to his crusty old professor, who is renowned for his razor-sharp legal mind.

Student: "Sir, do you really understand everything about this subject?"

Professor: "Actually, I probably do. Otherwise I wouldn't be a professor, would I?"

Student: "OK. So I’d like to ask you a question. If you can give me the correct answer, I will accept my marks as it is. If you can't give me the correct answer, however, you'll have to give me an "A".

Professor: "Hmmmm, alright. So what’s the question?"

Student: "What is legal but not logical, logical but not legal, and neither logical nor legal?”

The professor wracks his famous brain, but just can't crack the answer. Finally he gives up and changes the student's failing mark into an "A" as agreed, and the student goes away, very pleased.

The professor continues to wrack his brain over the question all afternoon, but still can’t get the answer. So finally he calls in a group of his brightest students and tells them he has a really, really tough question to answer: "What is legal but not logical, logical but not legal, and neither logical nor legal?”

To the professor's surprise (and embarrassment), all the students immediately raise their hands.

"All right" says the professor and asks his favourite student to answer

"It's quite easy, sir" says the student "You see, you are 75 years old and married to a 30 year old woman, which is legal, but not logical.

Your wife has a 22 year old lover, which is logical, but not legal. And your wife's lover failed his exam but you've just given him an "A", which is neither legal, nor logical."