Judicial activism has become a universal pejorative, a rare point of agreement between Red and Blue America. Conservatives and liberals alike condemn courts for overturning policy decisions they support. Both sides would reduce the judiciary's constitutional scrutiny of the actions of other branches of government -- a role it exercises not too much, but far too little.

To be sure, courts deserve criticism when they exercise legislative or executive powers -- ordering taxes to be raised, assuming control over school systems or prisons, giving regulatory agencies broad lawmaking authority. But better to call this behavior what it really is, not "activism" but lawlessness. By contrast, judicial activism -- defined as courts holding the president, Congress, and state and local governments to their constitutional boundaries -- is essential to protecting individual liberty and the rule of law.

While judicial activism is the subject of spirited attack, the far greater problem is judicial abdication of its core constitutional duty to protect individual rights. Courts routinely apply a presumption of constitutionality to most governmental enactments that skews the playing field against individuals whose rights are violated. Far worse, courts have read out of the Constitution vitally important protections of individual rights, such as the constraints against government interference with the sanctity of contract and the privileges or immunities of citizenship.

Properly wielded, a court gavel can be David's hammer against the Goliath of big government. Among our governmental institutions, courts alone are designed to protect the individual against the tyranny of the majority -- and against special interest groups with outsized influence. For better or worse, the courts are the last line of defense against government running roughshod over individual liberty.

Clint Bolick is a senior fellow at the Goldwater Institute and author of David's Hammer: The Case for an Activist Judiciary. A longer version of this article originally appeared in the Wall Street Journal.