In journalism, interviewing someone "off the record" means that the reporter cannot print quotes, even without giving the name of the source.

Are there laws or rules enforcing this? Or is it only based upon the reporter's good morality?

In general, are there laws forcing reporters to keep their sources confidential, kind of the same way as the attorney-client privilege can't be waived by the lawyer?

I know there are constitutional constraints about this in Sweden (because I read Millenium), but detailed info would be cool, specifically for the US jurisdictions.