John Oliver clearly explains the complicated fight between Apple and the FBI

For the past few weeks, Apple has been locked in a tense battle with the FBI over a dead terrorist suspect’s phone.

The fight is fairly complicated. It involves encryption, advances in modern technology, and long-running disputes about the right balance between privacy and security.

On Sunday, Last Week Tonight host John Oliver took a deep dive into the issue.

The fight began when Apple refused to help unlock deceased San Bernardino terrorist suspect Syed Rizwan Farook’s iPhone, citing concerns that providing the encryption key to the device could give the FBI a “master key” that could work on other people’s iPhones as well. The FBI has argued that Apple is being overly cautious and that the technology company could find a way to unlock just Farook’s phone.

At the heart of all of this is encryption, the code that helps keep our phones safe from intruders, but has also made life harder for law enforcement.

For Apple, the big concern is that weakening the encryption on its phones would weaken people’s protections and security not just against government intrusions, but even private individuals who could manage to steal or duplicate whatever key Apple makes for the FBI.

For the FBI, the primary worry is getting into Farook’s phone. It believes that Apple is exaggerating the risks. And it’s citing a 227-year-old law, the All Writs Act of 1789, to try to force Apple to cooperate.

It’s a very messy issue — one that could end up in the Supreme Court. Oliver does a good job combing through the details, so make sure to watch above.

For more, check out Tim Lee’s explainer on Vox.