Yahoo's general counsel said Thursday that the US government tried to force them to give up their user data in 2008 by threatening to fine them $250,000 each day they refused.

Although the company did end up giving up the information after a unsuccessful legal challenge, Yahoo said it fought the government on the order in secret court proceedings.

The company won a motion today to unseal those court records, which challenged the constitutionality of the broad data demand.

According to the Washington Post:

The documents, roughly 1,500 pages worth, outline a secret and ultimately unsuccessful legal battle by Yahoo to resist the government's demands. The company's loss required Yahoo to become one of the first to begin providing information to PRISM, a program that gave the National Security Agency extensive access to records of online communications by users of Yahoo and other U.S.-based technology firms.

The ruling by the Foreign Intelligence Surveillance Court of Review became a key moment in the development of PRISM, helping government officials to convince other Silicon Valley companies that unprecedented data demands had been tested in the courts and found constitutionally sound.

Yahoo, which was heavily criticized when information about PRISM was leaked by Edward Snowden, had until today been legally prohibited from detailing its efforts to fight the order.

The company detailed that chronology in a Tumblr post Thursday.

In 2007, the U.S. Government amended a key law to demand user information from online services. We refused to comply with what we viewed as unconstitutional and overbroad surveillance and challenged the U.S. Government's authority.

Our challenge, and a later appeal in the case, did not succeed. The Foreign Intelligence Surveillance Court (FISC) upheld the predecessor to Section 702 of the FISA Amendments Act. The Court ordered us to give the U.S. Government the user data it sought in the matter.

[image via AP]