It is forbidden to… You are not allowed to …
You are not permitted to…
It is prohibited to …
You must not …
You are not to…
You can't…
Examples:
You are not allowed to smoke in this area.
It is forbidden to swim here.
You are not to feed the animals.
It is prohibited to walk on the grass.
You must not tell anyone about it.
You must not leave the window open.
You are not permitted to be late.
