The 2006 Secure Fence Act specifically called for "two layers of reinforced fencing" and listed five specific sections of border where it should be installed. The new spending bill removes the two-tier requirement and the list of locations.
Duncan Hunter (R-CA) and Steve King (R-IA) aren't happy with the changes, and Minority leader Boehner's already placing blame on Congressional Democrats--though Sen. Hutchison (R-TX) seems to be one of the motivating figures behind this change.