The tech industry and the federal government have been in a long-running battle over so-called “National Security Letters,” which the FBI uses to obtain information about Internet customers—while also imposing a gag order that forbids the tech companies from even disclosing they received the letter in the first place.
But thanks to a 2015 law, Google and others are now able to shine a tiny bit of light on these letters and what they look like. On Tuesday, the search giant published eight of these letters in which FBI field offices in places like Buffalo and Dallas demand Google turn over information about Gmail subscribers. Here is a screenshot from one of those letters that shows what the demand looks like:
As you can see, some of the information, including the customer account, has been redacted. Nonetheless, the fact we can see these letters at all is significant because, until this year, companies have been forbidden from disclosing them or even mentioning how many they received. This is despite the fact the FBI has reportedly been sending out hundreds or thousands of these letters to companies like Google, Microsoft and Yahoo.
The letters are controversial because, unlike a search warrant, they do not require any approval from a judge. The FBI can just send them, along with a gag order, and companies must comply. There is almost no judicial oversight of the process.
Get Data Sheet, Fortune’s technology newsletter.
One reason Congress allowed this is because the letters do not force the companies to disclose the content of the Gmail (or hotmail or Yahoo mail) messages—for that the FBI does need a warrant. Instead, the Internet companies must turn over information about the email account, including who owns it and, importantly, the other people with whom the user has communicated.
While the letters, and the gag orders, can play an important role in helping law enforcement conduct sensitive terrorist investigations, the absolute secrecy surrounding them has long rankled tech companies and civil libertarians.
Now, there is a little less secrecy thanks to the 2015 law, which obliges the FBI to review whether there is still a good reason to maintain a gag order.
Google (GOOL) is the second company to publish National Security Letters. Yahoo (YHOO) became the first to do so this summer when it published three such letters in July.