As I write, Sen. Rand Paul (R-Ky.) has been speaking on the floor of the United States Senate for 7 hours and 33 minutes. Paul's "talking filibuster" is occurring during a floor debate on President Obama's nomination of John Brennan to the post of CIA director. However, the real issue here originates with a question Paul asked of the White House, and its subsequent response.
In February, Paul asked the Obama administration whether it believed it had the authority to order the killing of U.S. citizens on American soil. The administration already says it reserves the right to assassinate Americans abroad that it believes are engaged in terrorist activities, and has made good on this belief with the killings of U.S.-cleric Anwar al-Awlaki and Samir Khan in a drone strike in September 2011, and also Awlaki's 16 year old son weeks later (although the administration has denied he was the target).
Paul is especially concerned with the response he received from Attorney General Eric Holder on Monday. Holder left the door open just enough to allow the executive branch to justify the killing of U.S. citizens on U.S. soil without due process.
Right now Paul is doing what few Democrats have dared to do — oppose Obama's trampling of the Fifth Amendment rights of American citizens.