In Present continuous^x, Conditionals^x, Difference between^x

1) Do May / Might NOT (like CANNOT) express an interdiction = must not ? ex: ? CJ

Thank you very much, CJ, for your answers! Some more questions if you wouldn't mind: 1) Do May / Might NOT (like CANNOT) express an interdiction = must not ? ex: ? 2) Mrs James is in hospital and HASN’T BEEN ALLOWED TO have (and NOT “could have”) a cigarette after her meals. (correct ?) 3)...