A federal court is ordering Apple to break the security of its products by building a backdoor into one of its devices — an iPhone 5C belonging to one of the San Bernardino shooters. The controversial order, which was issued yesterday, marks the start of a brewing legal fight that could culminate in Congressional action on encryption. Until Congress tackles the issue head on, though, the question at hand is how this order is justified and whether it will hold up during the appeals process.

The FBI successfully got the order issued because of a law passed more than 200 years ago. The All Writs Act of 1789 allows federal courts to issue writs, or court orders, that require third parties to assist in the execution of another court order, like a search warrant. It’s only applied as a last resort. It’s previously been used to compel a telephone company to help install a pen register, for example.

While the AWA has been referred to in the past, this order drastically widens its scope. It’s one thing to require a company to assist in carrying out a search warrant, but in this case, the FBI is requiring Apple to build entirely new code to access the device in question, and part of that code would rely on Apple using its private key to authenticate it. This essentially amounts to the FBI requiring Apple to lie about its security checks, Nate Cardozo, staff attorney at the Electronic Frontier Foundation, told The Verge.

"No court has approved an order or law that would compel a company to do something or speak in a way that wasn't completely true," he said. "In this case, Apple is being compelled to create computer code that is false in a very meaningful way."

This is where Apple’s argument comes in. A specific exception made in the AWA is that it cannot require third parties to assist in ways that would be "unreasonably burdensome." By following this order, Apple could argue, it would place a burden on its reputation. No one will ever trust the security of their devices again, Cardozo said. "It’s an extraordinary burden — not just one of cost and time, but of a loss of good will in Apple."

But that argument could crumble, Susan Hennessey, a Brookings fellow, said. Regardless of Apple’s reputation, it's an American company and is therefore subject to US laws. However, one of the company’s strongest arguments will likely be the burden of creating something entirely new for the government.

"This is not sticking a key in the door and turning it," she said. "This is making the key, which falls beyond the reasonable task that underlies all writs."

Court orders are meant to assist the government in doing its job, not force companies to do the job entirely, she said.

"We’ve never seen an All Writs Act order that would force a company to not only do an amazing amount of work, but also to sacrifice its trust model," Cardozo said.

The government could come back and say that writs change over time with technology. They evolve along with the devices, and this recent order is a natural extension, Hennessey said. But that case has yet to be played out. As it stands, Apple has five business day to formally oppose the order, although it can ask for more time to do so. Once it opposes the order, the judicial process takes over, with it going first to a district court, and then progressing through the court system on appeals.

But Congress could throw a curve ball into the whole process by passing its own encryption bill that could mandate companies to build devices with backdoors built in. While the order affecting Apple impacts only one device, a Congressional law would impact devices across all brands. Cardozo believes this possibility is part of the FBI's motivation for carrying out the order through a public court, as opposed to under seal.

"That choice is not a mistake," he said. "The FBI wants not only public pressure on Apple but public pressure on Congress. The FBI kind of doesn’t care if it loses this fight if it puts pressure on Congress mandating that they give them a backdoor. They can’t lose."

Congress has been waffling back and forth on encryption bills for years. Just last week, Rep. Ted Lieu (D-CA) and Rep. Blake Farenthold (R-TX) introduced a bill to prevent states from passing their own encryption bills. As far as this order, Lieu said it brings up multiple questions.

"Forcing Apple to weaken its encryption system in this one case means the government can force Apple — or any other private sector company — to weaken encryption systems in all future cases," he said in an emailed statement to The Verge. "This precedent-setting action will both weaken the privacy of Americans and hurt American businesses."

Ultimately, just as Apple CEO Tim Cook wrote in his statement, the order facilitates public discussion and thereby the need for Americans’ opinions.

"There’s a growing understanding that this is the role of Congress because it’s the role of the people," Hennessey said. As the people’s representatives, the issue falls on legislators.