The Government Accountability Office (GAO), which investigates public expenditures for the US Congress, says a Post Office plan to drop Saturday mail delivery doesn't satisfy its legal obligations. In a letter, GAO General Counsel Susan Poling writes that an earlier rule requiring six-day delivery should be considered to extend into 2013, despite the Post Office's argument to the contrary. Since the 1980s, Congress has written in funding for the Post Office on the condition that it maintain the same service level as 1983 — which means six days of mail delivery a week. In 2012, that rule was extended, but the Post Office has said that since a later 2012 budget bill didn't specifically include the provision and the funds were never appropriated, it shouldn't be bound by that decision.

"The six-day delivery provision has been enacted into law every year since 1987."

Poling disagreed with that logic, saying a look at similar cases implied that Congress assumed the rule would continue to be in force. "The six-day delivery provision has been enacted into law every year since 1987," writes Poling, "and was enacted once again in the 2012 Appropriations Act." If that rule is maintained, the already struggling Post Office would face losing funds if it decided to drop mail delivery on Saturdays.

A Post Office spokesman, however, told The New York Times that the GAO decision "does not address" its plan to change delivery days starting in early August, since the decision was based partly on a temporary budget fix that will expire before then. However, the decision was always based on somewhat shaky legal ground, and another recent spending measure would also require the Post Office to deliver mail six days a week. Once that measure becomes law, the Post Office spokesperson says, "we will discuss it with our Board of Governors to determine our next steps."