When Captain America: Civil War was announced, many people doubted the movie would do the Superhero Registration Act. After all, most of the heroes in the Marvel Cinematic Universe have public identities, so forcing them to reveal them wouldn’t make much sense and it wouldn’t spark the Civil War the way it did in the comics. But the post-credits stinger for Ant Man confirmed a major element of Civil War is indeed being used.
In the final stinger of the movie, Cap and Sam finally find Bucky and his metal arm is stuck in a piece of equipment. The two debate who to call to help get him out, and when Stark is brought up they say, “the accords won’t let him help.”
That’s obviously referring to a government program to regulate superheroes, which is the Marvel Cinematic Universe version of the Registration Act in the comics. This scene was actually shot as part of Civil War, and Kevin Feige decided it would make a good credits stinger (like Thor’s hammer in Iron Man 2). That means the dialog between Cap and Sam is referring to the current state of the MCU during Civil War, when the “accords” have split the heroes into sides.
Going off of the comic, it’s easy to assume that Iron Man goes along with the government and supports these accords that regulate superheroes, while Cap is against them. It’s a good way to adapt the Registration Act from the original Civil War comic to the Marvel Cinematic Universe while preserving the conflict everyone can’t wait to see on the big screen next May.