First, Gannji and Enor are both
True Neutral, though Gannji leans a little more Lawful and Enor leans a little more Chaotic.
Second, they were absolutely
trying to kill Roy when Enor breathed lightning. A half-dragon's lightning breath does more lethal damage than 99% of the people in the world can withstand.
However, remember that in the Empire of Blood, it would have been totally legal to kill Roy on the spot for asking about a legitimate bounty. The only reason it became an issue is because Kilkil "lost" the paperwork.