In a country as politically divided as the United States is currently, a unanimous Supreme Court decision speaks volumes.  On January 27, 2017, President Trump signed Executive Order 13769, Protecting the Nation From Foreign Terrorist Entry Into the United States, which aimed to put into place different protocols for vetting foreign nationals from entering the country, who originated from six "Countries of Concern" which is a US State Department designation.  The six countries relevant to EO 13769 were identified and designated during President Obama's second term.  Detailed analysis can be found here. 

Unsurprisingly, there were multiple and almost instantaneous federal lawsuits filed in the west coast federal courts aimed at blocking the implementation of EO 13769.  Rapidly, the President issued a second order, EO 13780, also titled Protecting the Nation from Foreign Terrorist Entry Into the United States, which was aimed at addressing the concerns raised by the litigation.