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Congress held firm, and passed a bipartisan budget that denied any funds to construct a wall outside of Texas. But when Trump signed Congress’s budget into law, he announced that he was going to disregard its limits and take additional billions of dollars from the military for his wall.

Trump’s actions represent an unprecedented power grab. The Constitution is clear that only Congress has the authority to decide how to spend taxpayer funds. The Founders viewed this separation of powers as a key protection against tyranny. As James Madison wrote in The Federalist Papers: “The power over the purse may [be] the most complete and effectual weapon with which any constitution can arm the immediate representatives of the people.”

The Sierra Club and the SBCC then sued to block the wall, enlisting the American Civil Liberties Union, where I work, to take them on as clients. Their members live in, protect, and treasure the lands and communities along the southern border, which are threatened by construction. The administration conceded that these groups have “standing” to sue, which means that they face harm from the government’s actions and have a personal stake in the lawsuit.

Earlier this summer, a district court blocked the administration’s efforts to divert $2.5 billion for the wall—money that Congress originally appropriated for military pay and pensions, chemical-weapons disposal, and support for our allies in Afghanistan. The administration’s argument was that a particular transfer authority, known as Section 8005, gave it the power to redirect these funds.

But Section 8005 is restricted to transfers for “unforeseen military requirements,” and cannot be used to fund an “item” that Congress “denied.” As the district court held, Section 8005 couldn’t possibly apply here: Trump has been asking Congress to pay for a wall for years, and Congress expressly and repeatedly denied that request.

That government appealed the district court’s decision, arguing that the Sierra Club and the SBCC aren’t entitled to judicial review. Even before the appeal was decided, however, the administration asked for an emergency order allowing it to start immediately spending military funds on the wall. When the Ninth Circuit denied its request for an emergency order, the administration asked the Supreme Court to step in.

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And it did, issuing a temporary stay. In Friday’s order, a five-justice majority refused to even look at whether Section 8005 applied to Trump’s transfer of taxpayer dollars to the wall. Instead, the majority’s brief, one-paragraph order stated simply that the administration had shown “at this stage” that the Sierra Club and the SBCC could not get judicial review of whether the administration was unlawfully claiming a power under Section 8005. The words at this stage are key. To receive a temporary stay, the bar was lower than for normal court review. The government had to show only a “fair possibility” that it would ultimately prevail. Possibility does not mean eventuality.