Are you asking for a formal definition that could be put in code? Sorry, there just isn't one. The same laws which apply to stealing tangible things and cash a

Are you asking for a formal definition that could be put in code? Sorry, there just isn't one. The same laws which apply to stealing tangible things and cash also apply to stealing cryptocurrency. In the very unlikely event that the perpetrators came out and sued the Ethereum developers for violating their contract and taking "their" money back, a judge would look at the facts and then decide how the law applies to this particular case. IANAL, but I'm ready to bet that the thieves will go to jail for a while :-)