The ongoing battle between the United States government and Silicon Valley tech companies over encryption exploded last week when a federal judge ordered Apple to unlock an iPhone. In doing so, the government invoked a 227-year-old law signed by President George Washington, himself. But what does one of the United States’ earliest laws have to do with the latest in communications technology?

Related Content How the NSA Stopped Trying to Prevent the Spread of Encryption And Decided to Just Break It Instead

To make a long story short, Apple has so far refused to comply with government agents, who have demanded that the company helps break the encryption on the iPhone that belonged to one of the San Bernardino shooters responsible for killing 14 people in California, last year. Since the attacks, the F.B.I. has received a warrant for the information on the iPhone, but they have been stymied by its encryption, which is why they’re looking for Apple’s help. In an attempt to make Apple create a backdoor into the phone’s operating system, the U.S. government has invoked the All Writs Act of 1789.

The legal issues around the All Writs Act are complex, but at its core, it gives federal judges the power to issue orders to compel people to do things within the limits of the law, Eric Limer writes for Popular Mechanics. In its original form, the All Writs Act was part of the Judiciary Act of 1789, which established the federal justice system from the Supreme Court down to the lower federal courts. The All Writs Act allows federal judges the power to issue court orders, which makes sense considering that "writs" is an old-fashioned term for "formal order." At one point in history, writs were fairly common, but over the centuries, courts have tended to use them only in extraordinary circumstances where there are no other laws that apply to the situation at hand, such as this case, where the government wants access to information in a password-protected cell phone. The vagueness built into the All Writs Act has leant itself to new readings throughout American history, Laura Sydell reports for NPR.

"The law actually seems to be keeping up with technology by being so broad that we're just reinterpreting it all the time," Irina Raicu, director of the Internet Ethics Program at Santa Clara University's Markkula Center for Applied Ethics, tells Sydell.

The government has cited the All Writs Act in the past, from a 1977 ruling forcing phone companies to help set up devices that record all numbers called from a specific phone line to the Wireless Communications and Public Safety Act of 1999 which required all cellphone providers to be able to geolocate their customers’ phones. The writ does have its limits: a federal judge ruled in 2005 that the All Writs Act could not be used to force a phone company to allow real-time tracking of a phone without a warrant, Eric Lichtblau and Katie Benner report for the New York Times.

Whatever the result of this current case, the dispute will have major legal implications for the fight over encryption in the future. While the F.B.I. says the court-orderd bypass, which would have Apple create software to disable the feature that wipes the data on the phone after 10 incorrect password attempts, would only be used in this particular case, Apple’s chief, Timothy D. Cook recently fired off an open letter arguing that allowing this would set a dangerous legal precedent for user privacy in the future.

Editor's Note, February 24, 2016: This post has been updated.