If a thing is enforced, it is made to happen even though you did not choose it. Illness can mean enforced rest. A storm can mean an enforced night at a station. A rule you cannot escape can mean enforced silence. The feeling is: the situation, or some power outside you, decided, and you live with it. People also use enforced for a law or ban that is really made to stick, but this sense leans toward life events you cannot control, not only police. Though actually, students often meet enforce first as “make people obey a law”; here the -ed word quietly means “forced on you.”