I mean anything that would limit the U.S. in accessing any information available to them through the Patriot Act on any Canadian citizen overflying the United States. “Fetter” means that the United States actually would be under obligation, not simply under agreement under the terms of a letter from an ambassador or an understanding reached during a discussion. It would be something that would actually fetter their ability to collect or share this information.
On December 2nd, 2010. See this statement in context.