Require users to get a proper permit at the infringement of which they will be put into prison.
I am pretty sure it's not grammatical, or is it? Anyway, is there a better way to say this? I can't think of a better way, but there has to be.
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In the United States we would say "Require users to get a proper permit on pain of imprisonment” or “on penalty of imprisonment."
At the beginning of each trial day, Sergeant-at-Arms Michael Stenger will declare, "Hear ye! Hear ye! Hear ye! All persons are commanded to keep silent, on pain of imprisonment." - From "Do chatty senators really face jail time during impeachment?" on rollcall.com
Similar usages include "on pain/penalty of dismissal," "on pain/penalty of a fine," "on pain/penalty of deportation," "on pain/penalty of death," etc.
Another option would be "require users to get a proper permit or face the possibility of imprisonment."