A federal judge ruled Monday that the National Security Agency’s bulk collection of phone records likely violates the Constitution, in a major setback for the controversial spy agency.

U.S. District Court Judge Richard Leon granted a preliminary injunction sought by plaintiffs Larry Klayman and Charles Strange.

The ruling was the first major legal defeat for the NSA since former contractor Edward Snowden began exposing secrets about the NSA’s data collection over the summer.

Leon granted the injunction sought by plaintiffs Larry Klayman and Charles Strange, concluding they were likely to prevail in their constitutional challenge. Leon, an appointee of former President George W. Bush, ruled that the two men are likely to be able to show that their privacy interests outweigh the government’s interest in collecting the data. Leon says that means the massive collection program is an unreasonable search under the Constitution’s Fourth Amendment.

“The Fourth Amendment typically requires ‘a neutral and detached authority be interposed between the police and the public,’ and it is offended by ‘general warrants’ and laws that allow searches to be conducted ‘indiscriminately and without regard to their connections with a crime under investigation,'” he wrote.

He added: “I cannot imagine a more ‘indiscriminate’ and ‘arbitrary invasion’ than this systematic and high-tech collection and retention of personal data on virtually every single citizen for purposes of querying and analyzing it without prior judicial approval. Surely such a program infringes on ‘that degree of privacy’ that the founders enshrined in the Fourth Amendment. Indeed I have little doubt that the author of our Constitution, James Madison, who cautioned us to beware ‘the abridgement of freedom of the people by gradual and silent encroachments by those in power,’ would be aghast.” […]