On the same day of last month's proclamation allowing commercial fishing in the monument, Trump issued an order to boost the US commercial fishing industry by peeling back regulations and opening up harvesting in previously protected areas.
The monument was created by President George W. Bush in 2009 and consists of about 1.3 million square kilometres in the central Pacific Ocean. President Barack Obama expanded the monument in 2014.
A week after the April 17 proclamation, the US National Marine Fisheries Service sent a letter to fishing permit holders giving them a green light to fish commercially within the monument's boundaries, even though a long-standing fishing ban remains on the books, according to a lawsuit filed in a federal court in Honolulu.
The first longline fisher started fishing in the monument just three days after that letter, according to Earthjustice, which has been tracking vessel activity within the monument using Global Fishing Watch.
The Department of Justice declined to comment.
The lawsuit noted that commercial longline fishing, an industrial method involving baited hooks from lines 96km or longer, will snag turtles, marine mammals or seabirds that are attracted to the bait or swim through the curtain of hooks.
"We will not stand by as the Trump administration unleashes highly destructive commercial fishing on some of the planet's most pristine, biodiverse marine environments," David Henkin, an Earthjustice lawyer, said in a statement.
"Piling lawlessness on top of lawlessness, the National Marine Fisheries Service chose to carry out President Trump's illegal proclamation by issuing its own illegal directive, with no public input."
Designating the area in the Pacific Ocean to the south and west of the Hawaiian islands as a monument provided "needed protection to a wide variety of scientific and historical treasures in one of the most spectacular and unique ocean ecosystems on earth," the lawsuit said.
The lawsuit added that allowing commercial fishing in the monument expansion harms the "cultural, spiritual, religious, subsistence, educational, recreational, and aesthetic interests" of a group of Native Hawaiian plaintiffs who are connected genealogically to the Indigenous peoples of the Pacific.
