ICC judges issue arrest warrants against Shoigu and Gerasimov

It's complicated. Dual use infrastructure can become valid military targets. It's also easier to make claim military justification for a limited strike meant to aide a specific operation. But repeated strikes broadly on civilian infrastructure is terror bombing and pretty indefensible.

It was illegal before as well, it's just nobody really cared about Serbia, Afghanistan or Iraq (or any of the myriad of other warzones such as Libya).

At least in the case of Serbia though, an argument can be made that the NATO bombings back then were to stop a war of aggression in the first place.

That is not permitted if the target either doesn't have military value or collateral damage exceeds the proportional value of a military target.

Not only it's unnecessary, unlawful and immoral, it also means that you're bad at war.

A major part of WW2 strategy was Allied raids targeting Axis power plants, since electricity was a critical component for military factories (i.e., energy-intensive steelmaking). There was a mini-arms race around hydroelectric dam tactics—defensive nets to entangle bombs, vs. "bouncing bombs" that skipped across the surface of the water, circumventing the nets.

https://en.wikipedia.org/wiki/Operation_Chastise

The dam bombings in Norway, at Telemark, were extra special: that was a critical component of Hitler's semi-serious nuclear weapons program. Vast amounts of electricity were being secretly used to separate deuterium from water, on the understanding that was necessary to produce working nuclear fission reactors for the purpose of creating plutonium. (This was an error; the US correctly figured out that ordinary graphite was sufficient, for this type of nuclear reactor).

https://en.wikipedia.org/wiki/Norwegian_heavy_water_sabotage

(No implied commentary on the OP story).

Anything done by Russia is not permitted and considered to be war crimes

How is that remotely interesting to note? Surely you recognize that there’s a difference in culpability between the actions of an illegal invading force and an international peacekeeping mission aiming to stop a genocide?

As the ICC statement makes clear, the bombing of power plants and other energy infrastructure in and of itself is not a crime. It only reaches that level if the strikes are committed with the intent to cause civilian harm and suffering and are not justified by a military advantage.

The NATO bombing of power infrastructure in Serbia was investigated by the United Nations International Criminal Tribunal for the former Yugoslavia (ICTY). The ICTY prosecutors were satisfied with the evidence presented by NATO that the targeting was narrowly aimed only at infrastructure which specifically fed into key parts of the military air defence and command and control network, and that it had hit transformers and other easily replaceable elements rather than the main plants. [0]

So it was proportional, fulfilled a military purpose, and wasn't aimed at causing undue suffering of the civilian population.

[0] https://www.icty.org/en/press/final-report-prosecutor-commit...

“I’m afraid electricity also drives command and control systems. If President Milošević really wants all of his population to have water and electricity all he has to do is accept NATO’s five conditions and we will stop this campaign. But as long as he doesn’t do so we will continue to attack those targets which provide the electricity for his armed forces. If that has civilian consequences, it’s for him to deal with … [so] that water, that electricity is turned back on for the people of Serbia.” -- NATO spokesperson Jamie Shea during NATO aggression against the SRY. (He's also the person who coined the propaganda term "collateral damage" against civilian casualties.)

It can be said that pretty much everything NATO did in 1999. in SRY, Putin is now doing in Ukraine.