The nation's highest court will review legal challenge questioning automatic citizenship for those born in the US.

The US Supreme Court has decided to review a pivotal case that challenges a century-old principle: guaranteed citizenship for people born in the United States.

On the inaugural day in office this winter, President Donald Trump issued an executive order aiming to halt this practice, but the order was struck down by federal courts after legal challenges were filed.

The Supreme Court's eventual ruling will ultimately support citizenship rights for the children of foreign nationals who are in the US without authorization or on non-immigrant visas, or it will end them entirely.

Next, the court will set a time to hear the case between the administration and plaintiffs, which comprise foreign-born parents and their young children.

A Constitutional Cornerstone

For nearly 160 years, the Fourteenth Amendment has enshrined the rule that every person born in the United States is a citizen, with certain exclusions for children born to foreign diplomats and personnel of foreign military forces.

"All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States."

The contested directive sought to deny citizenship to the children of people who are either in the US without legal status or are in the country on non-permanent visas.

The United States is among about 30 countries – largely in the Americas – that provide instant citizenship to any person born on their soil.