Lysander Spooner

A Massachusetts lawyer and abolitionist, Spooner argued that slavery was unconstitutional and later went further: No Treason (1867 to 1870) claims the Constitution binds nobody, because nobody alive signed it, and taxation without individual consent is robbery. He also set up a private mail company to undercut the Post Office. His consent argument is still the sharpest challenge to any state's authority, and the easiest to dismiss as impractical.