Environmental groups are worried that the Trump administration’s proposed border wall could violate laws and threaten endangered wildlife. The Animal Legal Defense Fund, Defenders of Wildlife and Center for Biological Diversity challenged the president’s plan in court, but on Monday (December 3), the United States Supreme Court declined to hear the case, reports CNBC.

The organizations wanted the Supreme Court to reject a 1996 law signed by former President Bill Clinton that allows the executive branch to “waive environmental laws if those laws impede construction of barriers and roads near the border,” the news outlet reports. In 2005, the law was expanded to allow the Department of Homeland Security to “waive all legal requirements that could stand in the way of border construction.”

Now that the highest court in the nation won’t hear the challenge, a February 2018 ruling in favor of the government by U.S. District Court Judge Gonzalo Curiel stands. Judge Curiel gained prominence in 2016 when then-presidential candidate Donald Trump insisted he couldn’t be impartial in a class-action suit against Trump University because he is “Mexican.”

Nine Democratic members of the House of Representatives supported the environmental groups in their mission to stop the president from putting wildlife in harm’s way; the Center for Biological Diversity says the wall represents a “looming tragedy for the region’s diverse wildlife and people, as well as its rugged and spectacular landscapes.”

The proposed 2,000-mile border wall has been a signature issue for Trump’s presidency. It continues to be crucial element in his ongoing crusade against immigrants.