Must you go through customs when arriving from Puerto Rico?
If you are arriving from Puerto Rico in a country other than the
United States, you must go through Customs.
If you are arriving in a US airport from Puerto Rico, for
instance, if you are arriving in Miami, or New York, or Los
Angeles, you are on a domestic flight and will not be asked to go
through Customs.
If you started in Puerto Rico, you started from within the US.
If you started from another country, you went through US Customs
when you arrived in Puerto Rico.