To be fair to Russia (which I agree is absolutely the bad guy here), the war has moved on from being an outright invasion of a sovereign state into a fight in which Russia is also targeted - genuine Russian sites, as well as claimed ones. So whether they can legally use conscripts in this fight is probably answered.

I worked with a talented Russian gal for a few years. She was a geophysicist and we worked in the oil and gas software industry. She and her husband also a scientist, were both born in one of the "science" cities, built in southern Siberia. I also was acquainted with a Ukrainian gal who worked in the medical profession. Let me tell you, there was little love lost between the them. They never met one another, but judging from their comments and attitudes toward their respective nations, this war is going to color relations between the two for the next couple hundred years. The Ukrainians harbored hatred of the Russians for the Holodomor, the genocide of the Ukrainian Kulaks during collectivization of agriculture. Millions were starved to death in order for the Russian state to take their land. Bottom line is that they have very long memories. Even when the war ends, it will continue to be a flash point for generations.