I once got interdicted by AI. The guy circled around me shouting bold phrases, but he didn't attack, the colour which marked him was still orange and not red. If I fired, I'd be the aggressor.
It's a trick, so be wary of not falling into it.
However, there was another situation once. I followed an unknown signal and found an ASP. It immediately attacked me, but I think it didn't actually hit me first. I answered and of course had clean hits. I took it out and upon returning to Dahan I was destroyed.
So if you ask me, it is, or back then during Beta was a flaw in the system, because it seems only being actually hit first makes the attacker the bad guy and your defense justified, while in the real world the one who opens fire, regardless whether you get hit or not, is to be considered the aggressor. Or it was just a bug...
And by the way, if you don't want to risk anything, or have a more aggressive play style, you can deactivate the feature that notifies the authorities about criminal activities against you (and by that your own). But then you might not receive bounties for killing criminals.