Remove Diplomatic Immunity, OR Use International Law properly
It was somewhat of an outrage when Muammar Gaddafi was murdered by the rebels in a fairly horrific scene, when in reality he should have stood trial in a court of International Law. This is the kind of barbarity that should not happen anymore. He was captured, and would have had no difficulty being put on trial. He also now has the ability to become a martyr, and that could have some very dangerous repercussions.
The idea of removing diplomatic immunity is more difficult, and admittedly a bit more ill-advised, but my point is that a lot of the world's leaders need to stand trial for the clear violations of their country's constitution, and international law. The unconstitutional wars in the US for example that have been happening since the 50s, and the endless Western foreign manipulation into other country's leadership.