US Supreme Court agrees to review legal challenge questioning birthright citizenship.

The top court has will hear a landmark case that puts to the test a longstanding constitutional right: birthright citizenship for those born within US borders.

On day one 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 brought forward.

The Supreme Court's final decision will ultimately affirm citizenship rights for the offspring of migrants who are in the US undocumented or on short-term permits, or it will overturn those rights altogether.

Next, the judges will set a time to hear the case between the government and claimants, which include immigrant parents and their young children.

A Constitutional Cornerstone

For more than 150 years, the Fourteenth Amendment has codified the doctrine that all individuals born in the country is a US citizen, with specific conditions for children born to foreign diplomats 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 children of people who are either in the US illegally or are in the country on short-term status.

The United States is among about a minority of states – largely in the Americas – that provide automatic citizenship to anyone born on their soil.