The Sons of Liberty are an organization of Patriots that Johnny is exposed to through his connection with John Adams and John Hancock and The Boston Observer. The Sons of Liberty are technically criminals because they commit acts of treason and rebellion on a regular basis. They post placards and send secret messages under the cover of newspaper delivery. Throwing tea into the harbor is of course one of their most famous actions.
The actions of the Sons of Liberty might be seen as extreme, or even criminal. History judges them as heroes, but that is because they were successful and those same individuals became our founding fathers. So although they broke the law, they did so with a clean conscience and not for personal gain but in order to be free of England’s tyranny.