Does it make sense: "you can, but you may not"?

Question

I mean, both verbs here mean, you know, the same... right? How come, then, that one "can but may not" at the same time???

Explain to me that, please!

I'm a ESL speaker...

Thank ya!

, you know,

Answer 1

"You can" talks about the person's ability to perform a task."But you may not" means at that juncture due to some reason the person may be unwilling to perform the task.

Answer 2

It means that you have the ability to do whatever is under discussion but not the permission to do so.

Answer 3

Your sentence means

"It is possible for you to do this, but you are not allowed to do so".

There is a subtle difference  between "can" and "may".

"Can you speak English?

"Of course I can!"

"May I speak to you for a moment? "

"I am sorry, I can't talk now"

Answer 4

Can means to be capable of doing something, to be physically able to do something. You might, for example, be talking about jumping into the river and I would be concerned for your safety. So to your question: "Can I jump into the river?" I reply: "You can [meaning that you are quite capable of doing so] but you may not [meaning that you don't have my permission to do so because it's too dangerous].

Some parents are very fussy about this and make sure that their children ask: "May I do something?" because there is in that form an implied request for permission, whereas "Can I do something?" means "Am I able to do something?".  However, I think most of us break that rule in practice!