It is explained in the beginning of this story that the narrator is hassled by the Burmese. They despise him because he's a British official. He is disgusted at how the British treat the Burmese, yet he is obligated to do his job.
When it comes time to take care of the elephant situation, he finds himself stuck in a hard position. Because he is an officer, he has a gun and he can shoot it. That would be considered your "warrant" answer. His position gives him the authority (even though he doesn't really know what he's doing) to shoot the elephant. However, he realizes how important that elephant is to its owner. It is like a piece of machinery to them. Shooting it will set someone back quite a bit financially.
The assumptions are that because he is a British officer, he represents them and believes as they do. He doesn't though. That's both the conflict and the irony in this story. He doesn't not support what he represents, but he has to do his job. And in the end, he only shoots the animal because he couldn't stand to be laughed at and ridiculed.