A few years ago in the UK we had something similar introduced under the Crime and Disorder Act 1998. At the time their was alot of criticism of restricting mainly teens liberty, even though it could be applied to anyone.
Under the Act if anyone or a group of people acted antisocially, and it must be proven over a long period, they would be given an Anti Social Behavioural Order (ASBO) by the courts restricting movement. Many ASBO's were given to youths, in particular restricting groups of more than two or three youths from 'hanging around' certain areas where it has been known youths have caused trouble, or they may restrict certain troublesome youths with a curfew. In some cases they were applied to sections of known troublesome areas.
At the time it was introduced i was one of the ones agaist what i saw as restricting liberty.
But then one was introduced at a shopping precinct near to my fathers, where sometimes up to 50 youths would congregate at night. Over a six month period no more than 3 youths could be grouped together otherwise they could be taken to Court, for which there would be serious consequences. During that period many on my fathers estate felt safe to venture to the shops in the evening, the crime was reduced to almost zero and the neighbourhood became peaceful again. Since that time the youths have dispersed and there is no need for the ASBO to be applied, the neighbourhood is relatively peaceful again.
I think for such a thing as these ASBO's which in effect are curfews does affect an individual's liberty, but that has to be balanced against the liberty of the general public's need to feel safe and more importantly be safe in their communities.
Paul