yes.
at first, I had in "if you are too lawful, he won't trust you as you won't make such an agreement"
then... I thought "no, lawful guys always to what they promise, and good guys are not going to hire an assassin...they are good guys, so... lawful evil - lawful neutral is lawful, but they would respect agreements they make, even assassination contracts"
and so, I excluded the chaotic guys and the good guys from using the assassin.
because chaotic guys would not respect such an agreement (chaos is the opposite to law) and he won't contract with good guys, simply because they are good and would maybe try to lure him into a trap or so...