But since "valuable consideration" carries the threat of jail time, it has encouraged everyone involved to make an overly broad interpretation.

WSJ: Wait-Listed to Death

Congress has long included a ban on five-day-only delivery in its spending bills, but because the federal government is now operating under a temporary spending measure rather than an appropriations bill, Donahoe says it's the agency's interpretation that it can make the change itself.

WSJ: Goodbye Saturday mail? Postal Service plans cuts