President Donald Trump will watch the US supreme court hear a landmark case today weighing the constitutionality of his contentious bid to end birthright citizenship – an extraordinary and possibly unprecedented move for the nation’s highest office.

Trump signed an executive order on his return to the White House decreeing that children born to parents in the United States illegally or on temporary visas would not automatically become US citizens.

Lower courts blocked the move as unconstitutional, ruling that under the Citizenship Clause of the 14th Amendment nearly everyone born on US soil is an American citizen, AFP reported.

“All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States,” the amendment states. It does not apply to persons who are not subject to US jurisdiction – foreign diplomats, for example, and sovereign Native American tribes.

“I’m going,” Trump told reporters Tuesday when asked about the supreme court hearing. He had attended the investiture ceremony of his first supreme court justice nominee, Neil Gorsuch, in 2017, months into Trump’s first term.

But it would be an exceptional milestone for a sitting president to be present for oral arguments in a case their administration is actively arguing.

The Trump administration argues that the 14th amendment, passed in the wake of the 1861-1865 Civil War, addresses the rights to citizenship of former slaves and not the children of undocumented migrants or temporary visitors.

Trump’s executive order is premised on the notion that anyone in the United States illegally, or on a visa, is not “subject to the jurisdiction” of the country and therefore excluded from automatic citizenship.

Trump will attend the supreme court hearing from oral arguments from 10am ET today. He is then due to deliver an update on the Iran war in an address to the nation at 9pm ET.

In other developments:

• Trump signed an executive order seeking to restrict mail-in voting across the US with a series of new requirements, including the establishment of a national voter list.

• The move was unprecedented and likely unconstitutional, according to experts. The Brennan Center said in response, “He has no lawful authority to write the rules that govern our elections. He tried a year ago; we sued him; we won. A year later, he has tried again. He can expect the same result.”

• Several states and Democratic officials criticized the order, describing it as an illegal attack that amounted to voter suppression ahead of the midterms, and said they will take legal action to stop the president, including California.

• Trump continued to fume over today’s ruling from a US judge that halted the construction of his $400m White House ballroom, and sharply criticized the decision during a press briefing and on social media.

• Pete Hegseth lifted the suspension of the crew of the military helicopters that hovered near the home of singer Kid Rock, and said there would be no investigation.