An effort by Louisiana’s Jewish community to bar nitrogen gas as an execution method was blocked by a conservative legislative committee on Tuesday. Alabama was the first state in the nation to use the gas earlier this year. Since then, several Republican-led states have added the method, prompting a backlash by opponents who say it is inhumane. Members of the Jewish community in Louisiana have another reason for rejecting it: They say it invokes trauma from the Holocaust, when the Nazis used lethal gas to kill millions of European Jews. “I cannot remain silent against a method of execution that...