It can't. Everything about Civil War from the ground up makes it bad to adapt into a movie. This is why I didn't want Marvel Studios to do this.
Think about it. The Superhero Registration Act. Does anybody know exactly what the act entails? And I mean everything. The various writers of the the Civil War arc did not. It would seem obvious that the SRA is just a registration act. To which, I ask, what are our superheroes registering. Are they just on a database like the sex offender registry? To they have to register their powers in order to use them? Hell I can tell you why that's not going to work thanks to a little movie called X-Men. In the beginning of that movie Jean Grey is arguing with Senator Kelly about how the Mutant Registration Act is going to work. He mentions that we license people to drive cars or use guns, to which Jean tell him we don't regulate people to live. How you gonna stop someone from using a power when they don't control it? Or is the Superhero Registration Act a draft? In that case: Inacting a draft is virtually impossible in this day and age. Hell, this law wouldn't work because you need a war in order to inact a draft and what the hell kind of war would be going on in the MCU for there to be a draft on superheroes? This why when the government enacts a law, the texts and details of that law are extensive. To cut down on loopholes and misunderstandings that could get the law thrown out later.
Not to mention: The Superhero Registration Act is an act passed by Congress. THE US CONGRESS. This law could potentially be useless everywhere else outside of America, rendering at least one of the cast moot. And yes there are ways to make a law that was made in America, relevant across the globe. Trade agreement and UN Resolutions are a few that come to mind. But that would still leave holdouts. And who in west hell wants to sit through CBM that is literally 2 hours of parlimentary procedure and a godawful civics lesson. Not me.
If they're smart the SRA is made irrelevant to the plot. The law is overly simplistic, and let's be honest people, would die on the House floor. Constantly. Regardless of how much support the law had. It can't work in practice.