Whether or not Russia is a Protocol I party doesn't particularly matter here as the war crime at issue is viewed now as a matter of customary international law and is explicitly within the jurisdiction of the ICC; Rome Statute Article 8, 2.(b)(iv)
The same ICC the USA has a law on the books to invade the Netherlands if it charges US troops? Russia isn’t a signatory either. It’s edifying to observe that only the losers ever get tried for war crimes. A major nuclear power may fail to win a war, but it can’t lose one except if everyone loses.
OK, but Russia withdrew from the ICC. And Ukraine has signed but not ratified. And as Russia can veto a U.N. Security Council resolution referring a crime to the ICC, I'm not sure how this happens? And it seems Russia is not a party to the Rome Statutes either.
Doesn't matter for ICC jurisdiction over war crimes committed in Ukraine, because Ukraine, while not a state party, has acceded to voluntary ICC jurisdiction for war crimes and crimes against humanity on its territory from 21 November 2013 forward. (If you are relying on Wikipedia, it seems to systematically omit mention of voluntary jurisdiction.)
> And as Russia can veto a U.N. Security Council resolution referring a crime to the ICC
A UNSC resolution is not required; for cases where the ICC would have jurisdiction, it can begin investigations on the initiative of the prosecutor with permission of the ICC judiciary, or on referral of a state party (which need not be directly involved.) After the ICC prosecutor announced the intention to seek permission for an investigation, based on both a completed preliminary examination which found sufficient indication of ICC-covered war crimes and crimes against humanity before the recent escalation, as well as additional concerns arising from the recent escalation on his own initiative, but noted that a state-party referral would streamline the process, 39 state parties to the Rome Statute submitted referrals relating to the situation in Ukraine to the ICC.
This is either a plan for malice or it's incompetency, either way it's not good.