I agree with Ineffable that the most important case of the period was Gitlow v. New York. However, I disagree that its lack is what tied Martin Van Buren's hands. Van Buren was rather spineless. His own words were: ""Your cause is just, but I can do nothing for you; if I take up for you I shall lose the vote of Missouri." Note that he didn't say that the U.S. Constitution prevented him from helping the Saints; he didn't want to lose the next election! The Missourians were committing theft, rape, and murder. Those are not acts which require Constitutional approval to curtail. What makes those things less likely to happen today isn't the Fourteenth Amendment or Gitlow v. New York. It's the availability of mass media and the concomitant public scrutiny.
What makes Gitlow v. New York important is the major contribution it made to the erosion of federalism. While in some cases it might seem better to have a powerful federal government which can squash local initiatives, on the whole it is a bad idea. There needs to be checks and balances between the state and federal governments. But the trend over the last 150 years has been to diminish state governments and empower the federal government. This is dangerous no matter which side of the political spectrum you're on. And that's more serious than anything that could come from recent or near-future developments of Korematsu v. United States and its impact on the War on Terror and President Obama's response thereunto.
Most Important Supreme Court Case of 1920–1950
Moderator: Marduk