In "Minority Report" - a brilliant short story by Philip K. Dick and a decent movie by Steven Spielberg starring Tom Cruise - one can be arrested for a "future crime." Psychics inform the police of crimes about to happen, and the would-be perpetrator is arrested just before the act.
Police in Texas are now arresting people for the future crime of being drunk in public. In San Antonio police are now raiding bars for patrons that they feel are likely to do something stupid while under the influence.
Note, at the time of the arrests, the "criminals" are merely sitting in a bar, drinking away their sorrows. They've not yet gotten behind the wheel of an automobile. They haven't started any fights. They haven't even walked down the street singing "Danny Boy" loudly and out of tune.
All they've done to get arrested was the very legal act of purchasing a drink from a licensed vendor. I'll agree that it's fair for police to watch people driving away from bars to make sure they're okay to drive. But this goes beyond close enforcement, and even beyond prevention, into a category of enforcing a form of morality that is not in line with the law.
Public safety is important, but let's leave the "future crime" enforcement to the science fiction writers.