What is an example of judicial activism?

The most recent example of judicial activism was the case of Perry v. Schwarzenegger, a 2010 decision by federal judge Vaughn R. Walker overturning California's constitutional amendment to ban same-sex marriage. In spite of the voters' approval of such a ban on same-sex, Judge Walker overturned the amendment, primarily based on his interpretation that the Constitution implies a "right to privacy," and thereby nullifying the will of the California electorate. Judge Walker's decision is currently under appeal.