You can do a common law contract without doing commerce.
Commerce is regulated by the Uniform Commercial Code which is controlled and governed by the (Roman Cult owned and operated) United Nations through their UNIDROIT statute.
Currently 64 countries, have adopted the UNIDROIT Statute, including the United States, Canada, the United Kingdom, most of Western European countries and many others.
UNIDROIT is located in Rome about 100 yards from the Vatican (the Roman Cult).
Another name for the UNIDROIT statute is Private International Law.