The Supreme Court on Monday refused to hear a case arguing that a key law giving President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE authority to build a border wall is unconstitutional.

Conservation groups, led by the Animal Legal Defense Fund and the Center for Biological Diversity, argued that the Illegal Immigration Reform and Immigrant Responsibility Act of 1996’s provision giving the Homeland Security secretary nearly limitless authority to waive laws in the name of building border protection infrastructure like walls is unconstitutional.

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The groups said the provision violates the Constitution’s separation of powers, a principal that reserves legislative power for Congress and prohibits the executive or judicial branches from writing laws.

“Section 102’s waiver and jurisdiction-stripping provisions unconstitutionally consolidate the power to make, enforce, and review laws in the Executive branch,” they said in an August petition to the high court, arguing that only Congress has the power to change laws and it can’t delegate that power to the executive branch.

The Trump administration argued that the legal provision at issue is sufficiently specific to be allowable under the Constitution.

The 1996 and subsequent amendments to it give the Homeland Security secretary the power to waive any law — not just environmental ones — in order to facilitate building border infrastructure like fences and roads.

The Trump administration has used the power a handful of times to upgrade and repair border fencing, waiving dozens of laws each time pertaining to environmental standards, religious protection and other policies.

The conservation groups sued over two such waivers, but a federal court in California ruled that the waivers were constitutional. The groups then appealed directly to the Supreme Court.

The case was denied along with dozens of others in a list issued Monday, without explanation by the nine justices, as is customary.

Trump has also promised to build a wall along the southern border, although Congress has not yet funded the project because Democrats have refused to allow it. Trump has recently floated shutting the government down by allowing funding to lapse if Congress does not provide money for a wall.