Three environment and animal advocacy groups are throwing their weight behind a lawsuit challenging the Trump administration's decision to declare a national emergency in order to build a border wall.

The Center for Biological Diversity, Defenders of Wildlife and Animal Legal Defense Fund submitted a joint lawsuit over the weekend arguing that the Trump administration lacked authority to use the emergency funding in such a manner and was unlawfully redirecting funds to build the U.S.-Mexico border wall.

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“The only emergency here is Trump’s assault on the Constitution,” said Brian Segee, a senior attorney at the Center for Biological Diversity, in a statement.

“Separation of powers is at the heart of our democracy and the power of the purse is a critical check on the president. Trump’s authoritarian attempt to build his destructive border wall is a flagrant abuse of that constitutional structure. If he gets his way, it’ll be a disaster for communities and wildlife along the border, including some of our country’s most endangered species.”

Animal Legal Defense Fund Executive Director Stephen Wells argued that wildlife is not being taken into consideration with the plans to finish the remaining more than 1,000 miles of border wall.

“Many species of animals, including endangered species, are put at risk by this project, and all alternatives that protect wildlife and the environment must be considered by law. We will continue to pursue all legal avenues to assure the law is upheld,” Wells said.

Conservation groups warned Friday that they were against Trump’s border wall emergency plan and would likely be taking action. They hammered Trump's proposal, saying it will have negative effects on the region's ecosystem and wildlife.

“A wall that divides communities, blocks wildlife migration, disrupts water flow and destroys delicate park ecosystems is not the solution to border security and immigration challenges,” said Theresa Pierno, president and CEO for the National Parks Conservation Association, in a statement.

The budget deal that Trump signed on Friday increases the funding for the border wall to build approximately 128 miles. However, with the emergency funding, Trump hopes to gain up to $8 billion to finish the remaining portion of the project.

With their lawsuit, environmental and animal rights groups join a number of states, including California and New York, and the American Civil Liberties Union that have already sued the Trump administration over the decision, setting up a likely lengthy legal battle.