Those who pass through this gate without permission will be prosecuted.

One word substitute is Trespassers.

Bypassers: one who or that which bypasses.
Culprits: a person who is responsible for a crime or other misdeed.
Absconders: a fugitive who runs away and hides to avoid arrest or prosecution.
Thoroughfares: a road or path forming a route between two places.
Trespassers: a person entering someone's land or property without permission.