This study analyzes activist behavior of Supreme Court justices in 132 decisions which struck down congressional statutes as unconstitutional in 1789-1990. Analysis of the justices' activist rates and liberalism scores demonstrate that these votes are ideologically based. Integrated models containing personal attribute and case factor variables are constructed to explore the votes as activist behavior. The same models are also tested with a new dependent variable constructed to measure the nullification votes as liberal votes. The models which explain the votes as ideological responses better explain the votes than the models which explain the votes as activism or restraint. The attribute variables offer better explanation in the late 20th century models and the case factors offer better explanation in the early period models.