The Supreme Court's 5-4 decision holding that corporations and unions can spend unlimited amounts of money in election campaigns is a stunning example of judicial activism by its five most conservative justices. In striking down a federal statute and explicitly overturning prior decisions, the court has changed the nature of elections in the United States. At the same time, the conservative justices have demonstrated that decades of conservative criticism of judicial activism was nonsense. Conservative justices are happy to be activists when it serves their ideological agenda.
Since Richard Nixon ran for president in 1968, a central feature of Republican and conservative rhetoric has been to attack judicial activism. The phrase is never defined with any precision and has often been used to refer to decisions that conservatives simply don't like. But if judicial activism has any meaning, it surely refers to decisions that overturn laws and overrule precedents. In contrast, judicial restraint occurs when courts defer to the other branches of government and follow precedents.
By this definition, judicial activism can be good or bad. Brown vs. Board of Education was activist in that it declared unconstitutional laws in many states requiring the segregation of the races in education. To do so, the justices overruled a 58-year-old precedent upholding such laws. But virtually all agree today that Brown was one of the greatest moments in Supreme Court history.
To conservatives, though, the phrase "judicial activism" has come to mean any decision with a liberal outcome.
The conservative majority, which in recent years has dramatically limited free speech in other areas -- such as for government employees and for students -- was willing to expand the free speech of corporations. There is no way to see this other than as the conservative justices using judicial review to advance the traditional conservative ideological agenda.