From the same article[1] I quoted in another reply:
Theophilus Parsons, first Chief Justice of Massachusetts, explained:
The people themselves have it in their power to resist usurpation, without an appeal to arms. An act of usurpation is not obligatory; it is not law; and any man may be justified in his resistance. Let him be considered a criminal by the general government, yet only his fellow citizens can convict him; they are his jury, and if they pronounce him innocent, not all the powers of Congress can hurt him; and innocent they certainly will pronounce him, if the supposed law he resisted was an act of usurpation.
Or, as Patrick Henry put it:
Why do we love this trial by jury? Because it prevents the hand of oppression from cutting you off. This gives me comfort ” that as long as I have existence, my neighbors will protect me.
[1]: http://www.counterpunch.org/2003/02/05/a-guide-to-surviving-...