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.
More litigation followed, including a petition for certiorari to the U.S. Supreme Court for review. In a unanimous decision, the Court upheld portions of Executive Order 13780 in the case Trump v. International Refugee Assistance Project, et al. The Court stayed the injunctions imposed by the lower federal courts which sought to block the EO, but limited to the scope of the EO to temporarily prevent entry into the United States by any foreign national of a country identified in the EO who has no bona fide relationship with a person or entity in the United States. In other words, the Court agrees with the President that the President does have authority to issue Executive Orders which determine who can and cannot enter the United States.
Interestingly, Justices Thomas, Alito and Gorsuch wrote separately that they would have upheld a total and complete ban as initially proposed by the President.
You can read the entire text of the Supreme Court's decision below.