Data mining by the National Security Agency has left many American feeling paranoid, in light of reports that the agency shares its findings with the Justice Department if there's evidence of a crime -- or that NSA agents are using it for their own amusement (not to mention the fact that the Obama administration is using private information supplied to the IRS and other agencies for political purposes).

Even members of Congress are worried that the NSA is spying on them.

Those fears are justified, says law professor Glenn Reynolds, proprietor of the popular Instapundit blog.

In USA Today on Monday, Reynolds argued that the NSA's data collection program threatens the separation of powers in the federal government, and the Constitution itself.

"But if the federal government has broad domestic-spying powers, and if those are controlled by the executive branch without significant oversight, then the president has the power to snoop on political enemies, getting an advantage in countering their plans, and gathering material that can be used to blackmail or destroy them," he wrote. "With such power in the executive, the traditional role of the other branches as checks would be seriously undermined, and our system of government would veer toward what James Madison in The Federalist No. 47 called 'the very definition of tyranny,' that is, 'the accumulation of all powers, legislative, executive, and judiciary, in the same hands'."

There's no proof that's happened so far, but given Obama's tendency to do whatever he thinks will benefit him politically, as we've seen with Obamacare, who would believe it couldn't?