Change your preferences here.
Prevents the opposing team from using any moves that the user currently has in its moveset. The effect lasts until the user switches out or faints. If the user's moveset changes (eg. via Transform) the opposing Pokemon will not be able to use any of the newly acquired moves. This move cannot be blocked by Substitute.
Imprison has little competitive use in singles since conditions required to use this move effectively are too hard to come by. There are a multitude of strategies in singles and you can't guarantee Imprison will be useful every match—the moveslot might be better used for something else. In doubles, however, Imprison is useful for stopping Trick Room, among other strategies.