The American Civil Liberties Union (ACLU) filed a challenge this week to a warrant in Washington that sought to gather the private Facebook data of Dakota Access pipeline protesters.

The warrant, which was granted by a judge, asked for the “messages, photos, videos, wall posts and location information” of the protesters, and even allowed for data to be gathered on people who merely interacted with the Facebook group. Police are searching for the info because of a protest on February 11 that blocked part of an interstate highway, causing a four-mile traffic jam. Officials contend the protest caused a five-car pileup.

The ACLU has challenged the warrant, claiming it violates both the First and Fourth Amendments of the Constitution.

“Political speech and the freedom to engage in political activity without being subjected to undue government scrutiny are at the heart of the First Amendment,” ACLU attorney La Rond Baker said. “The Fourth Amendment prohibits the government from performing broad fishing expeditions into private affairs.”

“Seizing information from Facebook accounts simply because they are associated with protests of the government violates these core constitutional principles,” Baker continued.

Law enforcement officials are using Facebook more and more to (legally) spy on citizens like this, so it’ll be interesting to see how the ACLU’s case plays out. But no matter what the outcome, it always pays to remember: be careful which groups you join and what you post.