This could have happened any number of ways: his parents called the
cops, or he was being unruly in some way such as yelling out the window
so as to disturb the peace, or making the wrong kind of phone calls, or
drinking on the front porch in public view, or something else. One thing
for certain is that there is much more to know than the fact of drinking
in his parents' house.
I recall only one instance of this in 35 years as a PA resident, where
the parents allowed their underage kid to have a booze party in their
house with all his underage buddies on the "better here than somewhere
else" theory, the party got loud and rowdy, and neighbors called the
cops. It is otherwise pretty routine for parents to allow their
underage kids to drink at home here, such as a glass of wine with
dinner, and of course nobody cares and nobody gets arrested for
anything resembling responsible drinking at home regardless of age. In
this case, which made the news big time, it is likely that the wild
party would have only been given a warning except that the parents got
beligerent about insisting that they should be allowed to have wild
underage drinking parties in their home and refused to stop the party,
essentially forcing the police to stop it for them.
Now if you want something curious, how about the chap who told his
doctor he drank 6 beers a day, the doc reported it to the PA
Department of Motor Vehicles (reporting any medical condition which
could impair driving is required by law), and his drivers license was
permanantly revoked without any hearing despite a perfect driving
record. The same thing happened to someone else who told his doc he
ocassionally smokes a bit of pot. These stories also made the news
big time, so now no one admits to their doctor how much they drink or
if they use any illegal drugs.