Because it's a war?

It is wrong as a person those anything can be admitted because it is a quarrel.
Two Britons and a Moroccan sentenced to death by pro-Russian court in separatist part of Ukraine.

Three foreigners were judged to death, after accusing them of being "mercenaries" for Ukraine. The three -- British citizens Aiden Aslin and Shaun Pinner, and Moroccan national Brahim Saadoune -- were foreign fighters who had been captured in the Ukrainian city of Mariupol by Russian forces in April.

Russia is the only country that considers the DPR independent. The international community does not recognize the region and its institutions, and considers the territory to be part of Ukraine. Independent watchdog groups have long accused the separatists of a dismal human-rights track record and ill-treatment of prisoners.

All foreign volunteers to be members of its armed forces and to be lawful combatants entitled to treatment as prisoners of war under the Geneva Conventions.

The judgment had absolutely no legitimacy. They are prisoners of war. This is a sham judgment with absolutely no legitimacy.