twitter @paulkrugman Trump, Donald J Kyrsten Sinema United States Politics and Government Douglas G. Brinkley Mattis, James N Johnson, Lyndon Baines US Politics Immigration Posse Comitatus Act (1878) Illegal Immigration U.S. Donald Trump Posse Comitatus Act Sinema, Kyrsten Jim Mattis Defense Department US Military United States Defense and Military Forces Brinkley, Douglas G Lyndon Baines Johnson Pentagon Immigration and Emigration nytimes.com