CE. He doesn't expect his officers to obey the law, but his personal commands. His service to the Empire is one of duty to the Emperor, personally, and because of his desire for power. He's a classic tyrant... both chaotic and evil, willing to overturn any law on a whim if it suits his personal desire.
Threaten to murder an on-duty military officer? Check. Conspire against his own master, knowing his master is in turn conspiring against him? Check. Violate galactic law and customs of diplomacy? Check. Ignore the chain of command? Check. Pledge his loyalty to Sidious, simultaneously planning to overthrow him? Check. Execute underlings without the benefit of a court-martial? Check.
People seem to have this idea that Chaotic individuals don't wish to rule others. That's not true at all. A Chaotic individual, as a ruler, expects their personal commands to be carried out, to the letter. If they declare that anyone wearing purple is to be flogged, anyone wearing purple is to be flogged. Why? Because they said so, and they are in charge. A Neutral individual's commands would be in service to their goals as ruler... for instance, Sidious, as a Neutral Evil individual, issues commands that further his personal power and frustrate his enemies. He expects the chain of command to be generally followed, but makes exceptions when useful. A Lawful Evil individual values hieararchy. Tarkin is a good example of LE. He gets annoyed when Vader tries to kill one of the other officers... they have work to do! Those Rebels aren't just going to go and kill themselves, you know. He also chooses to remain on the Death Star, despite being informed of the danger. Why? Sure, because he's arrogant, but also because it would be INCONSISTENT with his belief in himself as a courageous soldier.