Even though we don't agree, it seems like you have a good understanding of the constitution. I mistakenly thought that you might be one of the FReepers who wwere being hypocritical with their constitution talk.
No...one of the things you see a lot is liberals (and libertarians) arguing for federalism when it benefits their particular issue and conservatives arguing the opposite (for instance, the Partial Birth Abortion Ban), and vice versa when the terrain is reversed. I'm just being honest. However, it's difficult to argue what is and what is not 'Constitutional' these days. It kind of depends on whether or not Sandra Day O'Connor has taken her Metamucil.
From what I've read, there have been about three different working interpretations of the Constitution throughout American history. The last major shift was in 1937, the 'switch in time that saved nine', where much of the New Deal was upheld. I believe the 10th Amendment was finally finished off for all practical purposes in 1940, but I'd have to look that up. I'm a little foggy on that.