I vote for a Vasari envoy thats more than a little fond of sending down phase missles when the guy on the other end of the comms gets a lil "snippy", or just hurling them out the embassies airlock.
The Vasari are jerks, but they're also pragmatists. For one thing, they wouldn't waste valuable phase missiles on an unshielded target. For another, executing someone would be wasteful, and they don't have time for such foolishness. A Vasari who went around executing valued citizens for no good reason would probably be spaced for treason.
Thirdly: why execute someone when you can punish them in creative ways?
In their ten thousand-plus-year history of Empire, surely the Vasari have come up with creative ways of ensuring the obedience of valued citizens.