Clause 61 of the Magna Carta
Freeman on the land is a form of pseudolegal woo that holds that being governed and what normal people understand to be "laws" are optional.
Freemen believe that we are all subject to a massive international legal conspiracy perpetrated for the profit of the elites, but you can hack the system if you just use the right form of words. You do not have to pay taxes, debts, mortgages, etc. because we were all deceived, and if you say the right form of words this fact will be accepted.
They insist that the government is a corporation, are obsessed with maritime law, and call themselves things like "John of the family Smith." Essentially, they're hilarious and somewhat less threatening sovereign citizens.
No freeman arguments have ever succeeded in court, instead attracting fines, asset seizures, contempt convictions and criminal records. This won't stop freemen from claiming they work.