Earlier this month Sen. Rand Paul (R-Ky.) told an audience of conservatives that the legal philosophy known as judicial restraint has been an abysmal failure throughout American history. So Paul offered an alternative: The Supreme Court should stop deferring to the other branches of government and should instead spend more time striking down government infringements on individual liberty. "I'm a judicial activist when it comes to the New Deal. But I'm also a judicial activist when it comes to Brown [v. Board of Education]. I think the [Supreme Court] was right to overturn state governments that were saying separate but equal is fine," Paul declared.

The response to Paul's speech has been instructive. Conservative law professor and former George W. Bush administration official John Yoo, for example, attacked Paul's "immature views on politics and the Constitution," arguing that "Paul's claims about judicial activism raise fundamental doubts about his positions on social issues."

On the left, meanwhile, Vox's Andrew Prokop faulted Paul for "voic[ing] his support for an infamous and long-obsolete Supreme Court ruling asserting that 'liberty to contract' was a fundamental Constitutional right."

For conservatives like Yoo, the problem with Paul's speech is that he explicitly endorsed the Supreme Court's 1965 ruling in Griswold v. Connecticut, which struck down a state law banning the use of birth control devices by married couples on the grounds that it violated their right to privacy. According to many conservative legal thinkers—including both the late Robert Bork and current Supreme Court Justice Antonin Scalia—the Griswold Court had no business interfering with the state's broad power to regulate morality and private sexual behavior.

For liberals like Prokop, the problem with Paul's speech is that he endorsed the Supreme Court's 1905 ruling in Lochner v. New York, which struck down a state law limiting the working hours of bakery employees on the grounds that it violated the Due Process Clause of the 14th Amendment. Liberals dislike Lochner because they think the Court had no business interfering with the state's broad power to regulate economic affairs.

What these two views share in common is that they each support what amounts to virtually unchecked majoritarian rule over certain aspects of American life. For conservatives, judicial deference means that lawmakers get the last word when it comes to banning birth control and prohibiting "homosexual conduct." For liberals, judicial deference means that lawmakers get the last word when it comes to bulldozing private property in the name of eminent domain. Each approach demands judicial passivity in the face of its preferred forms of government action.

Rand Paul, by contrast, is offering a third way, something that we might call a principled libertarian approach. "If we believe in judicial restraint we presume the majority is correct. We presume that laws are constitutional until we can prove otherwise," Paul observed. But "maybe we should start with the presumption of liberty…. Maybe we should be presumed to be free."

To say the least, Paul's approach is at odds with the reigning pro-government orthodoxies on both the legal left and the legal right. No wonder he's got both sides running scared.