The nation's highest court agrees to review case challenging citizenship by birth.

The US Supreme Court has agreed to take on a significant case that puts to the test a longstanding guarantee: birthright citizenship for people born in the United States.

On day one in office this January, President Donald Trump issued an executive order aiming to end the policy, but the order was subsequently blocked by federal courts after legal challenges were brought forward.

The Supreme Court's eventual ruling will either affirm citizenship rights for the offspring of foreign nationals who are in the US undocumented or on non-immigrant visas, or it will overturn them altogether.

Next, the court will schedule a date to hear arguments between the administration and claimants, which include immigrant parents and their young children.

The 14th Amendment

For more than 150 years, the 14th Amendment has enshrined the rule that anyone born in the country is a US citizen, with specific conditions for children born to embassy personnel and members of foreign military forces.

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

The challenged presidential order sought to deny citizenship to the children of people who are whether in the US in violation of immigration law or are in the country on short-term status.

The United States is one of about 30 countries – primarily in the Western Hemisphere – that grant instant citizenship to all those born on their soil.