National advocacy groups. On May 27, some of the most influential national groups who support broad immigration reform asked the Obama administration not to take executive action until the House has had more time to work out a legislative solution. The letter was signed by the SEIU; the US Conference of Catholic Bishops; the National Immigration Forum; the Leadership Conference on Civil and Human Rights; the liberal evangelical group Sojourners; and the conservative Hispanic group the National Hispanic Christian Leadership Conference. These groups' highest priority is broad or comprehensive immigration reform, to overhaul the immigration system as a whole — which is something only Congress can do.