Apple CEO Tim Cook is defying a US court order to help the FBI access the encrypted phone of Syed Farook, one of the terrorists who killed 14 people in San Bernardino, California last year.  The hang up is over the way investigators are demanding the Cupertino giant break into the mobile.

The FBI has Farook's phone and legal permission to search its stored data, which is a really good idea considering the carnage of 2 December.  Farook and Malik murdered 14 of his coworkers at a county health department holiday party before he and his wife Tashfeen Malik were gunned down by police.

But investigators can't get past the passcode.  To break into Farook's phone, the FBI is asking/demanding Apple write a piece of malware that won't be limited to opening the iPhone 5C running iOS 9 in question; it will be able to be used again and again and again on other phones regardless of operating system. 

Mr. Cook warns that complying with the order would entail building "a backdoor to the iPhone", creating "something we consider too dangerous to create".  In an open letter to Apple customers, Cook goes on to say "such a move would potentially render tens of millions of devices vulnerable".  In other words, Apple can't comply without screwing over every other Apple customer who relies on encryption.

"Essentially, the government is asking Apple to create a master key so that it can open a single phone," the Electronic Frontier Foundation wrote in a statement supporting Apple.  "And once that master key is created, we're certain that our government will ask for it again and again, for other phones, and turn this power against any software or device that has the audacity to offer strong security."

The FBI's case rests on the All Writs Act of 1789.  The government is increasingly using this 18th century law to try to force tech companies to turn over user data (other things that were legal in America in the 18th Century: Slavery, beating women, killing indigenous people, child labor, generational debt, et cetera).  But although the AWA is somewhat broad, it can only force a company to do something if it's not an "undue burden".  Apple's case will rest on whether it can prove that being forced to maim its own security systems and customer guarantees is an "undue burden". 

And if Apple can be coerced, so can Google, Microsoft, Facebook, and all of the other tech companies, big and small.