If you blinked, you missed it.

Christmas came early for Marvel fans, via the trailer for Captain America: Civil War. It picks up after the post-credits scene from Ant-Man, centering on Falcon (Anthony Mackie), Captain America (Chris Evans), and a subdued Winter Soldier/Bucky Barnes (Sebastian Stan) and featuring an all-out, hero-versus-hero brawl that climaxes with Bucky and Cap pummeling Iron Man (Robert Downey Jr.). Throughout the trailer, we're reminded that Cap and Bucky are friends, and that their friendship is something the government and Iron Man don't approve of. Cap is essentially defending a public enemy.

But Civil War isn't that simple, nor does its plot focus solely on Captain America's personal relationships. There's a major clue pertaining to the world beyond Cap and Bucky folded into the trailer, but it appears so briefly that you might've overlooked it.

Pay special attention to the scene in which General Ross (William Hurt) is talking to Cap about Cap's vigilante status.

"You've operated with unlimited power and no supervision," Ross says. "That's something the world can no longer tolerate."

The scene could be misdirection, but it appears Hurt is speaking directly to Captain America. The camera then cuts to someone (Hurt) passing a document to Captain America. But there's little trickery going on here. The person receiving the document has painted fingernails and is wearing rings — so it's probably Scarlet Witch (Elizabeth Olsen) or Black Widow (Scarlett Johansson) if Hurt is indeed talking to the Avengers:

The document is labeled "Sokovia Accords," and according to an eagle-eyed Redditor, its full title is "Sokovia Accords: Framework for the Registration and Deployment of Enhanced Individuals." Sokovia is the country that Ultron attacked and then levitated in an attempt to wipe out the world in Avengers: Age of Ultron.

In the Marvel Cinematic Universe, there's an established idea of holding Avengers accountable for the damage they've caused. Going by that logic, Sokovia's name is being invoked as part of a superhuman registration act — a piece of legislation that will make people with superpowers comply with the wishes of the government.

Falcon refers to the Sokovia Accords by name in Ant-Man's post-credits scene:

"Who knows if the Accords will let him [Iron Man] help," Falcon tells Cap.

The Sokovia Accords are a slight tweak on the comic book source material. Written by Mark Millar, Civil War's inciting incident is a reality television superhero fight in which innocent humans are killed. In the upcoming film, that's being swapped for an Avengers-centric event — either the global fallout from Age of Ultron or a new event that employs the name Sokovia as a reminder of the Avengers' power.

While the friendship of Bucky Barnes and Captain America will no doubt play an integral role in Civil War, we shouldn't overlook how the potential registration act that will pit Avenger against Avenger — even though the trailer may have wanted us to.