A substantial part of why foreign flagged merchant vessels get easy access to ports is that they are "known" to not be armed.
We wouldn't let a <pick a foreign country not too friendly with us> warship steam into Boston Harbor. Same country's oil tanker or cargo ship? Come on in.
We wouldn't let a <pick a foreign country not too friendly with us> warship steam into Boston Harbor. Same country's oil tanker or cargo ship? Come on in.