The nation's highest court will hear case questioning automatic citizenship for those born in the US.

The top court has decided to review a landmark case that puts to the test a longstanding guarantee: guaranteed citizenship for individuals born on American soil.

On his first day in office this winter, President Donald Trump enacted a directive aiming to halt this practice, but the move was subsequently blocked by federal courts after lawsuits were initiated.

The Supreme Court's eventual judgment will either affirm citizenship rights for the infants of foreign nationals who are in the US undocumented or on non-immigrant visas, or it will nullify them completely.

Next, the judges will schedule a date to hear oral arguments between the administration and the suing parties, which include immigrant parents and their young children.

The 14th Amendment

For over a century and a half, the Fourteenth Amendment has codified the doctrine that anyone born in the nation is a US citizen, with exceptions for children born to diplomats and members 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 challenged directive sought to refuse 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 – mostly in the Americas – that award instant citizenship to any person born on their soil.