Because Steve was just as likely to listen to some idiots at the UN as he was to whoever was in charge of him in the Army, or Nick Fury. He talks about being a soldier, but you and I both know he didn't have the discipline to succeed in the normal chain of command. Steve does what he thinks needs to be done, damn the consequences, and damn actually thinking about it ahead of time. Which isn't to say that he isn't damn good at succeeding at it, just that it isn't always the smartest way to do things.

And being controlled by the UN? You'd better believe that was politics, and Steve doesn't play that game, either. He thinks that being enhanced by the serum gives him the responsibility to protect and help people, and he does that how he sees fit. And he's not wrong, and lord knows I agree with him on that aspect of the Accords, too.

[Sam sighs, and takes a long drink of his shitty coffee, leaning against the cabinet.]

But in the end, it all hinged on Bucky. The Accords would've prosecuted him - would've killed him, first, if we hadn't gone to Budapest to help. [Well. Bucky probably would have escaped and survived without them. Sam's not sure on that one.] So Steve set himself against them, because he wasn't gonna let anything or anyone harm Bucky. And, God help me, I followed, because that idiot needs someone with a brain by his side.