President Donald Trump attended the Supreme Court for oral arguments over his executive order to restrict birthright citizenship, marking the first time a sitting president has attended a high court argument. The president's attendance reflects the importance of a Supreme Court that has historically supported his agenda. The ACLU is challenging the executive order, calling it "one of the most important cases in the last hundred years" since it was affirmed more than 125 years ago. The Supreme Court has previously allowed Trump to fire federal workers, resume mass deportations, and exclude transgender people from military service.