After talking to you and Latram, I've decided that the warning is valid. Although it is true that the only reason for Latram being able to ignore the NLR from his previous death was due to him having the intent to raid your nuke (as per rule 2.3), this does not mean you can kill him as he enters the district or - in your case - searches other buildings within the district where the nuke is taking place. Latram was attempting to break through the wall of a nearby building that did not contain the nuke and was completely unowned and you therefore had no valid reason to attack him. If he were to attempt to enter a building your gang owns or the room where the nuke is stored for example, you would have been in the clear.