Quick 질문 about Harry Potter and the Goblet of 불, 화재 (Movie): **Contains spoilers if not seen movie 또는 read book**

First of all, I don't think the Unforgivable Curses are illegal 또는 that something will happen to 당신 if 당신 do one of them. Its just..well unforgivable. Now its Moody in disguise, he himself is an auror so he can use it whenever he wants. Keep in mind that the student doesn't know if its illegal so they can't tell Dumbledore 또는 any other professor.

Good question. Yes those curses are illegal. However, Dumbledore has always done things his way. That scene is in the book and the movie. If 당신 recall from Order of the Phoenix (book), Dumbledore hired Firenze as a Divination teacher after Umbridge sacked Trelawney.
Most likely, no one did anything because no one at the Ministry knew until probably that summer. Dumbledore knew the whole time. He's the one that wanted "Moody" to show the kids those curses. Reread that scene in the book. It's the chapter headedby a picture of Moody.

Because the kids where to scared to tell him. Even if they did who would believe them?!

Dumbledore gave him the permission to

Yeah, Dumbledore was the one to tell Moody. And the students did know.. I believe it was commented (by Hermione, probably), that they were illegal, and that Moody could have been imprisoned.

It's illegal to use the spells on human beings, not to teach about them (or use them on spiders). The only one Fake Moody actually used on the class was the Imperius Curse, when teaching them to throw its effects off. Hermione did initially 질문 the legality, but Fake Moody said that Dumbledore had given him permission and that it'd be better that they get the practice even if illegal.