When Sen. Rand Paul (R-Ky.) told an audience of conservatives last month that judicial restraint was a failed legal philosophy that harmed liberty and expanded government power, he took sides in a long-running debate between libertarian and conservative legal thinkers. As I explain in my new book, Overruled: The Long War for Control of the U.S. Supreme Court, this debate originated back in the second half of the 19th century when Progressive lawyers and activists began urging the Supreme Court to defer to the popular will and uphold democratically enacted economic regulations. That Progressive approach ultimately triumphed during the New Deal period and has been part of the American legal mainstream ever since.

In the late 1960s, the influential conservative legal theorist Robert Bork embraced the Progressive approach. In Bork's view, the Progressives were right when they said the Supreme Court had no business overturning their economic agenda. But then Bork took the analysis one step further. The Supreme Court was equally wrong, Bork argued, when it sought to overturn conservative "morals" legislation, such as state laws that banned birth control or prohibited homosexual conduct. "In wide areas of life," Bork declared, "majorities are entitled to rule, if they wish, simply because they are majorities." For Bork, that meant the Supreme Court should defer to the will of those majorities and butt out of such disputes.

In the decades to come, numerous conservatives would rally to Bork's call, thereby forging something of a right-left consensus in favor of a deferential judiciary.

Libertarians favor a different approach. In the words of libertarian legal theorist Stephen Macedo, "When conservatives like Bork treat rights as islands surrounded by a sea of government powers, they precisely reverse the view of the Founders as enshrined in the Constitution, wherein government powers are limited and specified and rendered as islands surrounded by a sea of individual rights." In other words, the libertarians view the Constitution as a liberty document which places strict limits on majoritarian power while protecting a broad range of personal and economic freedoms. Whereas Bork (like the Progressives before him) wanted the Supreme Court to defer to most government action, the libertarians want the Court to actively police the other branches of government.

This debate is very much alive and kicking today. Writing at the Library of Law and Liberty, for example, conservative legal scholar Richard Reinsch recently complained that "the restrained vision of the federal judiciary that has for some time dominated the jurisprudence of right-leaning American legal theorists and lawyers in this country is now under fire." Why is it under fire? Because "many libertarian and classical liberal scholars" have persuasively championed a constitutional vision which asks the federal courts to protect unenumerated rights from government infringement. "Even George Will," Reinsch fretted, "has reversed his own prior position on judicial restraint to now favor 'judicial engagement' to protect so-called non-fundamental liberties and unenumerated rights from the rule of majorities."

Reinsch's colleague Greg Weiner, meanwhile, went on the offensive, making his own case for conservative judicial restraint.

"Rights are not inherently judicial claims. We are only accustomed to thinking of them that way," Weiner wrote. "It might be healthier and, crucially, ultimately better for liberty if rights claims were to be politically resolved."

In other words, according to Weiner, if a small business owner believes an arbitrary regulation is violating her right to economic liberty, that person should take her complaint to the ballot box, not to the courtroom. Let the majority decide if her right is worthy of political protection. The judiciary has no business getting involved. (Chief Justice John Roberts made the same fundamental point in his 2012 decision to uphold Obamacare. "It is not our job," Roberts declared, "to save the people from the consequences of their political choices.")

Writing at the Volokh Conspiracy, Georgetown law professor Randy Barnett offered a spirited libertarian rebuttal to Weiner's vision of conservative judicial deference:

[T]ell me a story about how an individual denied the right to braid hair without an expensive and time consuming cosmetology license can get her right vindicated in "the legislative process."…

What does this African American woman do who wants to braid hair for money? How does her right become part of the agenda of the state Republican and Democratic parties and their candidates for the state representatives or senators? How does she make "the rest of us" aware of her liberty being violated so they can vote Republican or Democrat accordingly? How does she get the public to place a greater weight on her lone right to pursue a harmless occupation than they do on the other policies advocated by Republicans or Democrats? When will "deliberate majorities" ever even hear her claim?…

I know of only one way for an individual to assert her claims against administrative government workers and boards and panels. By bringing a lawsuit that is then decided by a genuinely neutral magistrate. Bringing suit is hard. Bringing suit is expensive (unless supported by a public interest attorney). But bringing suit is possible. It is only possible, however, in a legal system that recognizes the existence of a third co-equal branch of government called the "judiciary."

What might this libertarian legal approach look like in practice? Rand Paul gave a good shorthand description last month. "If we believe in judicial restraint," Paul said, "we presume the majority is correct." But "maybe we should start with the presumption of liberty…. Maybe we should be presumed to be free."

For more on the long war over judicial restraint, check out my book.