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

The US Supreme Court has decided to review a pivotal case that puts to the test a longstanding guarantee: guaranteed citizenship for those born in the United States.

On day one in office this January, the President enacted a directive aiming to end birthright citizenship, but the move was subsequently blocked by lower courts after constitutional questions were brought forward.

The Supreme Court's final decision will ultimately uphold citizenship rights for the infants of foreign nationals who are in the US without authorization or on non-immigrant visas, or it will nullify those rights altogether.

Next, the court will calendar a session to hear arguments between the federal government and the suing parties, which comprise parents who are immigrants and their young children.

A Constitutional Cornerstone

For over a century and a half, the Constitutional amendment has established the rule that anyone born in the nation is a American citizen, with certain exclusions for children born to embassy personnel and members of occupying armies.

"Every individual 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 offspring of people who are either in the US without legal status or are in the country on non-permanent visas.

The United States is one of about a minority of states – mostly in the Americas – that grant automatic citizenship to all those born in their territory.