People from Iran, Libya, Syria, Somalia, Sudan and Yemen will face tougher US entry criteria as a controversial travel ban comes into force.
All refugees will also face tougher restrictions on entering the country as a key plank of president Trump’s agenda comes into force.
After a period of legal confusion, the Supreme Court upheld the temporary ban earlier this week.
The decision means people without “close” family or business relationships in the United States could now be denied visas and barred entry.
However, the judges provided a major exception.
Those who have “a credible claim of a bona fide relationship” with someone in the United States will still be allowed to enter.
The effect is that citizens of the affected countries with a close relative in the US, such as a spouse, parent, child or sibling, will potentially be allowed in.
After a last minute change, fiancés were also added to the list.
Those who already hold valid visas are not affected.
Dual nationals who travel on their passport from the unaffected country will also be allowed entry.
The court also approved a 120-day ban on refugees entering the US.
This allows the government to bar entry to refugee claimants who cannot prove the same ties to an American individual or entity.