¿Triste Navidad?

This case is a "twofer": not only does it involves a not-so-jolly dispute over copyright ownership of a holiday song; it also offers a refresher in Civil Procedure.

Here's the background: J. Walter Thompson ("JWT") secured a license from music publisher Peer International ("Peer") to use the song "Llegó la Navidad" in a 2016 holiday campaign for JWT's client Walgreens. After the campaign began, LAMCO, a music publisher, and ACEMLA, a performing rights society, came forward alleging that they (and not Peer) were the real owners of the composition and that Walgreens' campaign infringed upon their rights. Peer disputed these assertions, leaving JWT stuck in the middle.

To sort out the ownership question, JWT brought an interpleader action against LAMCO and ACEMLA, following which various claims for infringement and indemnity were asserted by and among the parties. The court disposed of the case quickly on the grounds of collateral estoppel (specifically, non-mutual col