In 2012, Congress reached a deadlock on a program that would have protected young immigrants from deportation if they had been brought to the U.S. as minors.
It's only January, but the U.S. Supreme Court has already tabled any hearings on the legality of the Deferred Action for Childhood Arrivals (DACA) program until at least this fall. Assuming the court sticks to its usual practices, that likely means no decision would become available until 2020.
From the beginning of his presidency, Donald Trump has been trying to issue a travel ban against people from certain nations -- mostly majority-Muslim ones. His original ban was overturned by the federal courts, however, largely because it appeared to be unlawfully discriminatory against Muslims. It was replaced with a second version that was also overturned.