The fundamental nature of targeting in the cyber domain is very different from conventional military standards. In particular, with enough recon, you can say to a high degree "Even though I released a worm that will destroy every computer it touches, I don't think it will kill anyone or cause permanent loss of function for vital infrastructure."
For example, if I have SIGINT captures that say that the major hospitals have decent backup and recovery plans, and the country itself has put their power companies on notice to be able to handle computer failures, I may have an understanding of my worm's projected effects that nobody else does or can.
Clearly another historical exception is if my destructive payload is only applicable to certain very specific SCADA configurations. Yes, there are going to be some companies that interact poorly with my exploits and rootkit, and will have some temporary damage. But we've all decided that even a worm that wipes every computer is not "destroying vital infrastructure" unless it is targeted specifically at vital infrastructure and in a way that causes permanent damage. Sony Pictures and Saudi Aramco do still exist, after all, and they are not "hardened targets".
The main issue is this: You cannot know, from the worm or public information, what my targeting information has told me and you cannot even begin to ask until you understand the code. Analyzing Stuxnet took MONTHS OF HARD WORK. And almost certainly, this analysis was only successful because of leprechaun-like luck, and there are still many parts of it which are not well understood.
So combine both an inability to determine after-the-fact if a worm or other tool was released with a minimal chance for death or injury because you don't know my targeting parameters with the technical difficulty of examining my code itself for "intent" to put International Law frameworks on a Tokyo-level shaky foundation. Of course, the added complication is that all of cyber goes over civilian infrastructure - which moots that angle as a differentiating legal analysis.
Many of the big governmental processes try to find a way to attach "intent" to code, and fall on their face. The Wassenaar Arrangement's cyber regs is one of them. In general, this is a problem International Law and Policy students will say is in every domain, but in Cyber, it's a dominant disruptive force.