How do you Enforce a Curfew?

So the Home Sec wants to give police stronger/new curfew powers to help in future riots. Just one question - how do you enforce a curfew?

Oh yes, by arresting people and removing them from the streets. If the police were in any position to arrest people and remove them from the streets during the first nights of rioting then they could have done just that. Fact is they weren't. So how would a new law help them if they can't enforce it?