This is checks and balances at work, ladies and gentlemen. Our president may be in favor of more direct control over the internet (the better to make his campaign donors in Hollywood happy with), but the president doesn't legally have the power to ratify a treaty. He can help negotiate it, but it's up to congress as to whether or not it goes through. Today, Congress did their job.
Edit: Except even the president was apparently against this one. Must have been /really/ bad, since he was in favor of SOPA and ACTA.