Read up on common law. It is more limited in our system than would be in a pure common law system because the courts have to defer to statutory law, and exhaust it, before resorting to common law implementation. Fair Use in copyright is an example. Statutory law was not specific on the issue, and it remained common law for decades (relying on "progress of the arts and sciences") before it became part of statutory law.
The prospect of American Courts deferring to foreign laws and customs in rendering decisions which impact our life is so chilling, so alien and so evil that any measures whatsoever to frustrate this are acceptable.
And I think Sam Adams, George Washington and Thomas Paine would agree.