Three weeks after Amtrak’s Empire Builder derailed along a remote stretch of track on Montana’s Hi-Line, killing three and injuring scores more, a dozen lawsuits have been filed by passengers injured in the deadliest railroad accident in the United States since 2017. But those lawsuits might run into trouble because of a never-before-tested clause recently added to Amtrak’s tickets that states passengers can’t sue the railroad in the event of an accident.