WASHINGTON — The US Supreme Court was set on Wednesday to consider the legality of President Donald Trump's directive to restrict birthright citizenship in the United States, a contentious plan tied to his efforts to curb immigration that would upend the long-held understanding of a key constitutional provision.

The justices would hear arguments in his administration's appeal of a lower court's decision that blocked his executive order directing US agencies not to recognize the citizenship of children born in the US if neither parent is a US citizen or legal permanent resident, also called a "green card" holder.

Trump plans to attend the arguments, according to his official schedule. It is believed that he would become the first sitting president to attend arguments at the country's highest court.

His policy violated citizenship language in the US Constitution's 14th Amendment as well as a federal law codifying birthright citizenship rights, the lower court found, acting in a class-action lawsuit by parents and children whose citizenship is threatened by the directive.

Limiting who qualifies for citizenship at birth is a top priority for the Republican president, who issued the order last year on his first day back in office as part of a suite of policies to crack down on legal and illegal immigration.

The 14th Amendment has long been interpreted as guaranteeing citizenship for babies born in the US, with only narrow exceptions such as the children of foreign diplomats or members of an enemy occupying force.

The provision at issue, known as the Citizenship Clause, states, "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside."

Govt's assertion

The administration has asserted that the phrase "subject to the jurisdiction thereof" means that being born in the US is not enough for citizenship, and excludes the babies of immigrants who are in the country illegally or whose presence is lawful but temporary, such as university students or those on work visas.

Citizenship is granted only to the children of those whose "primary allegiance" is to the US, including citizens and permanent residents, the administration has argued. Such allegiance is established through "lawful domicile", which lawyers for the administration define as "lawful, permanent residence within a nation, with intent to remain".

The administration has said that granting citizenship to virtually anyone born on US soil has created incentives for illegal immigration and led to "birth tourism", by which foreigners travel to the US to give birth and secure citizenship for their children.

The Supreme Court is expected to rule by the end of June.

Agencies Via Xinhua