As political theatre, Senator Rand Paul's marathon, 13-hour filibuster to protest the Obama administration's dreadful drone policy was gripping. While filibusters have become commonplace these days, they usually only involve a simple notice that one intends to filibuster, which then puts the onus on the other side to round up the 60 votes for "cloture" to end the threat. Paul, however, chose to filibuster the old-fashioned way, by standing on the Senate floor and speaking, as Paul said, "until I can no longer speak." While Paul's valiant protest captured the attention of the political twitterati and evoked comparisons to the classic Jimmy Stewart filibuster film, Mr. Smith Goes to Washington, it raised an important question few people were asking: Is the filibuster unconstitutional?

Surely not, you say. There's something quintessentially American about the lone dissenter, standing up for core principles of due process and the rule of law. Even the mighty Senate cannot silence his voice. The filibuster represents the best of American constitutionalism: protecting political minorities against the aggressive power of the majority. After all, how in the world could Jimmy Stewart be unconstitutional?

The answer, however, isn't quite so clear. While many people might assume that the filibuster is provided for in the Constitution, that document doesn't refer in any way to the tactic. The first Congresses did not have nor recognize a filibuster. Senators had the option of invoking a "previous question" motion, which by majority vote would end debate on whatever topic was being discussed. When that type of motion was eliminated in 1806, the reform wasn't intended to create the filibuster; it was, instead, instigated by the presiding officer of the Senate who thought the previous question motion wasn't needed in a house comprised of "gentlemen" who'd know when to move on. According to one historian of the filibuster, "Far from being a matter of high principle, the filibuster appears to be nothing more than an unforeseen and unintended consequence" of this house-keeping revision of the Senate rules.

Indeed, it would be decades before anyone realized that the rule change empowered senators to filibuster. The first Senate filibuster occurred in 1841, a full half a century after the Founding, and the issue was hardly equal in weight to the Obama Administration's refusal to rule out using drones against American citizens. It was over a bill appointing the publishers of Congress's newspaper, the Congressional Globe, and lasted ten days that involved, unlike today's talking filibuster, multiple senators taking the floor. This hijacking of the Senate was given the name "filibuster," after the Spanish word "filibustero," which refers to pirates, robbers, or privateers who break widely recognized rules. And the tactic remained exceedingly rare, with only fifteen more filibusters before 1900. These days, by contrast, there are more than 75 filibusters every year.

A number of legal scholars have argued that the filibuster is unconstitutional. They note that the Constitution's framers did not intend to permit dilatory tactics that interfered with majority rule. James Madison, who's credited as the primary author of the Constitution, wrote in Federalist 58 that requiring more than a simple majority to pass legislation would violate "the fundamental principle of free government." "It would no longer be the majority that would rule," he explained. "The power would be transferred to the minority." In his "Manual of Parliamentary Procedure," which was officially adopted by the early Congress, Thomas Jefferson wrote, "No one is to speak impertinently or beside the question, superfluously or tediously."