You are of course correct in using the term ‘executor’ as it relates to one “carrying out the legalities of”.
Now, were the comparison between ‘legislationer’ and ‘executioner’, a correction might be in order.
BTW, having the same reaction as Resettozero, I checked the definitions out of curiosity, and was surprised to notice no references to any form of punishment. To the contrary, here are a few synonyms: achiever, activist, organizer, worker, accomplisher.
Consider my word power increased, thanks to both of you.