UPDATED (11:25 am EST): The United States Postal Service says it will suspend regular Saturday mail delivery starting Aug. 5.

What is clear is why the USPS wants to scale back regular delivery by a day — doing so will save an estimated $2 billion a year. What’s not clear is if the agency can legally just stop stuffing mailboxes on Saturdays.  

“There’s a requirement that’s still applicable by Congress that the postal service still deliver six days a week,” says Gene DelPolito, president of the Association for Postal Commerce, a trade group representing businesses that rely on mail delivery. 

Since the post office will still deliver packages on Saturday, he says it might be able to get around the Congressional requirement on a technicality. According to DelPolito, what’s really happening is the Post Office is calling Congress’s bluff.

“They’re going to be facing off with each other, and I guess it depends on which one blinks,” he says.   

Jerry Cerasale, who is in charge of government affairs for the Direct Mail Association, says all of its 2,000 members will have to make some changes. For some, that will be a painful process. 

For others, “it will not, as long as the postal service maintains a service standard so they know when the mail is going to get into someone’s house,” says Cerasale.

 Cutting Saturday delivery will reportedly shave off about an eighth of the USPS’s total annual shortfall. And for the rest of us, it could mean two junk mail days a week.