On December 4, the U.S. Supreme Court allowed the administration's current travel ban targeting people from six Muslim-majority countries to go into effect. The ban, which is the third iteration of travel restrictions introduced by the administration, will remain in effect while legal challenges continue in lower courts. The nine justices, with two justices dissenting, granted the administration's request to lift two injunctions imposed by lower courts that had partially blocked the ban, implemented by the administration after the inauguration of President Trump in January.

The countries affected by the travel ban include Chad, Iran, Libya, Somalia, Syria and Yemen, and goes fully into effect for nationals of these countries seeking to enter the United States. The administration has advised that the travel ban is necessary to protect the United States from terrorism by Islamic militants. The ban also includes people from North Korea and certain government officials from Venezuela, but the lower courts had already permitted these provisions to go into effect.

The travel ban had been previously challenged in separate lawsuits by the state of Hawaii and the American Civil Liberties Union. The premise of the challenge against the ban claimed that it discriminated against Muslims in violation of the U.S. constitution and was not permissible under U.S. immigration laws. Previously, the lower courts had limited the scope of the ban to individuals without certain family connections or with formal relationships with U.S.-based entities, such as resettlement agencies and universities.

The Supreme Court, in its order, stated that the ban would remain in effect regardless of what the appeals courts rule until the justices make a decision whether to take up the issue on the merits, which is quite likely. The Court also instructed the appeals courts to decide the cases "with appropriate dispatch." Some exceptions to the ban include individuals from these targeted countries who may still apply for visas for tourism, business or educational purposes, and any applicant may request an individual waiver of the ban.

The administration issued a first travel ban in January, then issued a revised one in March after the first ban blocked by federal courts. The second ban expired in September after litigation and was replaced with the current version, which has been tailored with specificity for each country. The administration claims that a president has ultimate authority, based on the U.S. Immigration and Nationality Act, to decide who can enter the United States. Those who argue in favor of eliminating the ban claim that it violates a law forbidding the government from discriminating based on nationality when issuing visas.