The Right to Bear Arms

No freeman shall ever be debarred the use of arms.
Thomas Jefferson: Draft Virginia Constitution, 1776.

The last, most important check on government abuse of individual rights is an armed populace. A written constitution requires somebody to enforce it. Any mechanism built into the government, such as Checks and Balances, can be eventually bypassed by a determined government. Ultimately, the only thing that can prevent the use of force is the threat or use of greater force. To this end, the people are the ultimate check on government.

Only an armed population has the ability to overthrow a tyrannical government. Governments are well aware of this. In every dictatorship, ownership of guns is outlawed to the general populace. Before the Nazis went about exterminating their Jewish population, they needed to disarm them first. A state treads carefully when the citizens are armed.