If the men are volunteers for the Ukrainian military then they’re covered by the Geneva Conventions.
If Putin has them executed then he can find himself dancing at the end of a rope.
That’s how this works.
In any case, not our problem. If they chose to go to Ukraine and kill Russians, the consequences are on them. Unless you want to make them martyrs to justify further US involvement in Russian-Ukraine civil war.
All the talk about war crimes and trials is 🐴💩. If Russia executes them, they went there to kill Russians. What the hell you think the Russians will do. They went in harms way and found it. Harm. War crime trials are held by the Victors. Biden is an idiot not a victor. Putin May meet a Russian court for something someday but nothing US or NATO will do to him. I hope the two had fun, it may be awhile before they have some again.
That’s how this works.
Prepare to be disappointed.