@wtfftw
The thing is, Graham doesn't go for the kill versus the 00. If he were, Setsuna would have been dead after their first fight.
The fact that he's only out to duel(similar to an honorable duel between two samurai/European nobles) the 00/Setsuna means that he will never resort to the same tactics that Ali would resort to using.
Of course the A-Laws wouldn't warn Kataron. A real-life equivalent of them giving Kataron a heads up would be like the US military warning Al-Qaeda that they're going to bomb one of their bases at an appointed time using X amount of planes and bombs. Specially considering that Kataron is the 00 universe's equivalent of <insert major terrorist group name here>, the A-Laws high command wouldn't want to risk their soldier's lives by sending them into a terrorist stronghold.
You already gave the answer regarding Ali's ruthlessness in the fight against Setsuna and Tieria. Toying with your opponents and mocking them is something that could be described as ruthless. As I said before, Ali absolutely revels in fighting and killing. By toying with both Meisters, he's savoring the moment.
By the way, if the three alliances that existed prior to the Earth Federation's founding didn't have an equivalent of the Geneva Convention, you'd see people using NBC weapons left and right with zero regard as to the consequences of using those types of weapons.
PS
After the awesomeness of the Ion Cannon shot in ep.10, A-Laws has finally taken that crucial step towards being the big, bad military force that Sunrise, CB, and Kataron have been talking about.