La manera más usual de expresar órdenes y prohibiciones es el imperativo. Aparte de esto también se puede utilizar el verbo must (not) o una forma de have to.

verbo ejemplo
must I tell you, the men must be finished with the work by Monday noon.
have to You were told that you had to return home immediately.
must not One must not smoke in public buildings.

En este caso también hay un verbo pleno.

verbo ejemplo
to be (not) to We are to clean the kitchen after we used it. (imperativo)
You are not to take the dog into the supermarket. (prohibición)
to be not allowed to He is not allowed to have a cat in his apartment. (prohibición)
to not allow Her father does not allow her to have a motorbike. (imperativo)
to be not permitted to They were not permitted to use the toilet during the exam. (prohibición)
to be not supposed to People are not supposed to steal. (prohibición)