What exactly is "judicial activism"?

For both sides, judicial activism has come to mean “any Supreme Court decision that I disagree with.”

Actually though, don’t we want an active or engaged Court when it comes to upholding our constitutional rights and guarantees? Obviously courts should not invent “rights” out of whole cloth, or substitute their views for that of the Constitution. But, the Founding Fathers understood that sometimes legislatures go too far, that there will be a temptation to exceed the proper powers of government. When they do so, it is the proper role of the courts to rein them in.

Roger Pilon, the B. Kenneth Simon Chair in Constitutional Studies at the Cato Institute, has argued that conservatives too often “limit constitutional rights to those fairly clearly ‘in’ the document. . . . Thus for conservatives, if a right (is) not clearly ‘in’ the Constitution, it (does) not exist. What conservatives of the judicial restraint school have to come to grips with, then, is the full richness of the Constitution, including its natural rights foundations . . . for as the Ninth and Fourteenth Amendments make clear, the rights ‘in’ the Constitution are not limited to those the document plainly enumerates.” Indeed, he adds, were it otherwise, we’d have had precious few rights against the federal government before the Bill of Rights was added.