Bundy is in clear violation of a federal regulation. That's indisputable. What is disputable is on what authority the federal government can mandate that land once used by generations of family for grazing can no longer be used for grazing. Also at issue are states' rights. The Federal government certainly has the might, but does it have the right potestas?
Let's go ahead and concede for argument's sake that Bundy should have to pay certain fees for his cattle's past grazing and that the federal regulation was not unjust. And let's admit that Bundy is no hero or saint behind which one should start a movement. This is not a case that conservatives or libertarians should want to build an argument around. Let's further remind ourselves (and the Courts!) that we're to have a government of laws and not of men. Nonetheless, for conservatives and libertarians, the Cliven Bundy situation is a reminder of what taxes and government fees ultimately are equivalent to: FORCED labor. You pay or you'll PAY. For it is the government who holds the monopoly on military force. You don't pay taxes, they take taxes--by gunpoint if "necessary." That is why libertarians demand a strong justification for the purposes of taxation.
Well, the government almost has a monopoly on military force. The Bundy situation is also a reminder that an armed citizenry can make the government think twice about using its own superior military might to take what it wants when it wants. Does anyone really think that if U.S. citizens were unarmed that the Fed wouldn't have had its way and taken all that it wanted? If U.S. citizens were unarmed, would the U.S. government actually have to think seriously about whether to enforce its policies and at what cost?
Besides the advantage of being armed, which the Americans possess over the people of almost every other nation, the existence of subordinate governments, to which the people are attached, and by which the militia officers are appointed, forms a barrier against the enterprises of ambition, more insurmountable than any which a simple government of any form can admit of. Notwithstanding the military establishments in the several kingdoms of Europe, which are carried as far as the public resources will bear, the governments are afraid to trust the people with arms. And it is not certain, that with this aid alone they would not be able to shake off their yokes. -James Madison, The Federalist Papers #46.