Twice recently, I've seen a great Wonder Woman page posted, where she demonstrates the difference between her and Superman or Batman. I see it as a beautiful and concise piece of writing that adds depth to her character by not only showing that she is willing to kill, but also that her decision-making process is clear and that her actions immediate. The implication is that this could sometimes result in trouble for her, but that for the most part, it means that villains don't come back to bite her.
However, it has lead me to a question. Do cinematic Superman and Batman have a code against killing? I haven't seen Man of Steel, but I know that it was controversial that Superman's actions more or less directly result in innocent lives being lost. Similarly, I had a conversation with a (non comic-reading) friend after the release of The Dark Knight and we had a fundamental disagreement, because he was convinced that Batman had killed people. I realized that there was no explicit point where Batman says that he does not "cross that line". I don't need to see people die on screen to understand that the characters have died.
Is the result of the Christopher Nolan Batman series that Cinematic Batman and Superman simply do whatever they must? Do they have a code? I'm not sure anymore.