This strikes me as being completely unenforceable. Where is the line between legitimate PVP and harassment? How far does this go? So you interdict someone flying through supercruise in Open, interdict them, they combat log, then you see them again a few minutes later and interdict them again and destroy them. Next thing you know you've been banned for harassment, because the person thinks anyone doing PVP is a griefer, and doesn't understand this is a legitimate game mechanic. I don't see how FD can define the line on this except for always coming down in favour of the carebear.
There's that carebear wording again, and honestly it is baffling, I don't think I've seen anyone but a select few state that they dislike PvP on this whole topic.
But in your example, if you are interdicting them to say pirate them, you state demands and such, they vanish, then I wouldn't think you get in trouble in any situation, remember when GM/Devs handle subjects it isn't just a one way street, they aren't just going to go "oh he's reported for harassment" *banhammer* that's not how these things work, as it is not in any developers interest to ban those that do not deserve it, also might be one of the reasons that people get warned and such and why some may say "Devs aren't doing anything" because you can't see a warning.
However if you say, see a random person, you decide he needs to die, "because" and proceed to interdict and begin shooting at him nothing else, no other interaction, and he combat logs or dies. (note you should report combat logs)
You see him later, and do the exact same thing, you have nothing to gain from doing it other then wanting to see him blow up, and so you attack him again, and he maybe combat logs or dies again, then yeah you are working towards harassment.
And that is the key point I am trying to make, even the smallest amount of interaction, threaten him, tell him that this is your system (and obviously you shouldn't claim every system as yours), or maybe the system belongs to your minor faction and you don't want to see him here ever again, let him high wake out. If he refuses, you blow him up. If he complies, congratulations, you just made an impression on a person, good or bad, and improved the game by interacting with someone, and should you see him again in the system, you can of course chose if you want to give him a beating, maybe destroy some of his modules but not blow him up completely, or just destroy him, what have you, there are many options. And just like that you establish that, the system is "protected"/"enforced" or similar wording, by you, and that you only allow in certain people, heck the guy might even contact you and ask what he can do to be permitted into said system, and you can state a demand and maybe collect toll?
The only situation that begins to work towards possible harassment is the "Interdict, blow up" especially since seen from the victim side, that's all that happens, that's all your actions that you do, then yeah, then you look like a griefer, but if you interact, communicate with others, you know...play the game and like you are a part of it. Then it opens up for so many possibilities....