U.S. District Court Judge Richard Leon ordered the NSA to immediately stop vacuuming up domestic telephone records on Monday, writing that “the loss of constitutional freedoms for even one day is significant harm.”

But the order was limited to one plaintiff in the case: a California lawyer and his law firm.

Even so, the effect could be much more extensive. The government has previously argued that ending the collection of just one person’s telephone information records would be so technically challenging that it would be forced to shut the entire program down. On Monday afternoon, Department of Justice spokesperson Nicole Navas would only say that “the government is reviewing the decision.”

The NSA was already rushing to make its Congressionally mandated November 29 deadline to shut down the program and replace it with something more targeted.

An NSA order leaked by Edward Snowden in 2013 showed the FBI asking Verizon Business Network Services for three months’ worth of information about Americans’ phone calls: who’s calling who, when, and for how long.  That was the first time the public learned of what became known as the bulk telephony metadata program.

Leon’s preliminary injunction ordered the NSA to stop collecting records of attorney J.J. Little and his firm — the only plaintiffs who were customers of that particular company — and segregate any such metadata it had previously collected.

The bulk telephony metadata program, which the NSA said was authorized under Section 215 of the USA Patriot Act, included many other providers as well, but those have not been acknowledged by the government.

Congress decided to end the bulk collection program when it passed the USA Freedom Act in June, but gave the NSA 180 days to end it for good.

Leon’s order would force the NSA to stop spying on Little and his firm three weeks early — and maybe everyone else, too.

Leon had previously enjoined the program in 2013, declaring it “almost Orwellian,” but stayed his own order pending appeal “in light of the national security interests at stake and the novelty of the constitutional issues raised,” he wrote in Monday’s decision.

“I did so with the optimistic hope that the appeals process would move expeditiously,” he wrote. “However, because it has been almost two years since I first found that the NSA’s Bulk Telephony Metadata Program likely violates the Constitution and because the loss of constitutional freedoms for even one day is significant harm … I will not do so today.”

Leon noted the government’s position: that “the immediate cessation of collection of or analytic access to metadata associated with plaintiffs’ telephone numbers … would require the NSA to terminate the program altogether.” But he indicated that was not his problem. “Unfortunately for the government the court does not have much sympathy for these last-minute arguments,” he wrote.

The NSA can appeal to the D.C. Circuit Court of Appeals, which previously ruled against halting the program because the plaintiffs could not prove their records were collected. Now, after Little was added as a plaintiff, that obstacle has been removed.

“Judge Leon’s decision is a testament to the importance of the rule of law,” said Elizabeth Goitein, co-director of the Brennan Center’s Liberty and National Security Program. “This is an illegal program that violates the privacy of millions of Americans. It should not continue for another minute, let alone another three weeks. Judge’s Leon’s commitment to upholding the Constitution stands in stark contrast to the executive branch and FISA Court, which have been all too willing to play fast and loose with the law.”

Update at 9:22 p.m. ET: Hours after Leon’s decision, the government once again requested a stay, warning that complying would create “an intelligence-collection gap that could place national security at risk” and “would require months to complete”.