I've been out of banking for 20 years. I knew about SWIFT back then. It's not a secret organization and never has been. The nature of it's business is that it must have close working relationships with Government owned or controled central banks all over the world. Anybody with any knowledge of banking knows this. It's not a big deal.
If someone wants to move large amounts of money around the world through the traditional banking system they aren't going to be able to keep it secret from the United States, or the government of any other country that houses major banking institutions.
So it may have been classified, and before the NYT learned of it the fact that we were taking advantage of available information may have been secret.
But, even if terroists worldwide assumed the US is stupid and that they could use SWIFT to move money secretly, it's just not possible for the NYT to reveal a state secret. If they know it, then it's not secret anymore. They might have revealed classified information. But, it wasn't a state secret.
They told the US government they knew the secret and it was no longer a secret. The US response was basically to suggest that if they didn't print it we could all pretend it was still a secret.
They decided that's not really a good idea. I kind of agree with them. It's not a question of whether the public has a right to know. At least some of the public did know, and the US should not stick their head in the sand and pretend the public didn't know.
The point supporters of the Bush administration seem to miss is that it's not in the best interest of the United States to pretend something is secret when you know it's not secret.