[Grammar] He can't as prohibition

[englishhobby]

I think we can say: You can't sleep in class (meaning prohibition, not ability). (Compare: You can't park here.)
Can we say: He can't sleep in class (meaning prohibition, not ability)? (Compare: He can't park here.)
:?:
For example, during a lesson in some educational institution the director comes in and sees one of the students sleeping in class. The teacher explains that the student sometimes sleeps in class. The director tells the teacher that the student can't sleep in class - he must go home if he feels so sleepy. Is it possible?

 

[lotus888]

He can't sleep in class.
This is OK, but can be construed as inability to sleep.

Try:
He's not supposed to sleep in class.
He's not allowed to sleep in class.



--lotus

 

[englishhobby]

And if we change the sentence to He can't talk like this to the teacher, will it be less ambiguous? (The matter is that I need some clear example of prohibition beginning with He can't...)

 

[Matthew Wai]

'Mary can talk fluently in English but he can't talk like this to the teacher.'
Can it be construed as inability to talk fluently?

 

[englishhobby]

We need context, of course.