Vladimir Kara-Murza’s 25-year prison term for treason could be his death sentence. But advocates for one of Russia’s most prominent opposition figures say Canada has a powerful tool in its diplomatic arsenal that could save his life — honorary Canadian citizenship. Kara-Murza, 41, has suffered perhaps the harshest fate of all the dissidents in Vladimir Putin’s Russia. He has fought his way back from death by poisoning — twice. Last year, as others fled the country, he returned to Moscow to speak out against the invasion of Ukraine, knowing it would likely lead to his arrest. Now, he sits in...