WASHINGTON (AP) - The Supreme Court is siding with an Alabama company over the U.S. Postal Service in a patent dispute.

The justices said Monday that the government can't use a 2011 law to challenge a patent held by Birmingham-based Return Mail. The dispute involves a patent Return Mail got for a system that processes mail that gets returned as undeliverable.

The Postal Service initially expressed interest in Return Mail's invention but ultimately developed its own, similar system.

Postal Service officials tried to use the Leahy-Smith America Invents Act to challenge Return Mail's patent. The law says that a "person who is not the owner of a patent," can file a patent challenge using the law. But the justices ruled that the Postal Service isn't a "person" who can file a patent challenge.

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