No you can’t because those stains could have many causes not all caused by breaking the laws. They are also very subjective and you don’t want to execute someone just because is not Lilly white enough just because of a soul gaze, you need extra evidence especially if someone is already a group member.
That is why they wanted to invalidate his membership. You can do all kind of things with people who do not belong.
And Harry already had some stains from killing Justin. Just being stained is not breaking laws. The grey wardens are probably all a bit stained if you look at it from the perspective of someone whe kept his soul particularly clean.
While discussing this and some other stuff recently, it struck me that it’s interesting how matter of factly many responses are when discussing things that aren’t actually in the books. I don’t necessarily mean this answer, but in general.
Re: invalidating his membership
That’s why I speculated that Rashid could have had returning Dresden to the fold by obligating him with payment as an ulterior motive. Essentially, to keep him from having “other” status and so being the object of fear because, as evinced by history, frightened people are scary.
Having said that, I do have the feeling that the Merlin doesn’t currently want Dresden dead, though that is subject to change! It’s my speculation that, st the moment, he finds him more useful alive than dead. They could have a whole bromance buddy cop adventure, the Merlin and Dresden. That could be fun.