Execute as user is made up? It actually does exist but my guess was that it couldn't be used when executing policies.
Execute As (Transact-SQL)
Uh Oh... maybe I spoke to soon. I totaly missed the explination saying this was made up.
"Execute As" is definately a real thing! ;-)
"Execute As" is also definately not a permission!
You might be able to use this to test the Policy Alert if the User supplied has the ALTER TRACE permission. I realy have no way to test at this time....
Did you try this crafdenberg? If you can post some working script it would prove your point, but it would not make this command a permission.