US Supreme Court agrees to hear case challenging citizenship by birth.

The top court has decided to review a landmark case that puts to the test a century-old constitutional right: birthright citizenship for people born on American soil.

On the inaugural day in office this January, President Donald Trump enacted a directive aiming to halt this practice, but the action was struck down by federal courts after legal challenges were initiated.

The Supreme Court's ultimate ruling will either uphold citizenship rights for the infants of immigrants who are in the US undocumented or on short-term permits, or it will nullify them entirely.

Next, the justices will set a time to hear the case between the government and claimants, which comprise foreign-born parents and their newborns.

The 14th Amendment

For over a century and a half, the Fourteenth Amendment has established the doctrine that all individuals born in the country is a American citizen, with specific conditions for children born to embassy personnel and members of occupying armies.

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

The disputed executive order sought to withhold 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 among about three dozen nations – mostly in the North and South America – that provide instant citizenship to all those born on their soil.