You can’t defeat math. Encryption is available for anyone, not just Apple and if the phone wasn’t locked via Apple’s OS, it would be locked via a third party app that would be just as impossible to unlock and whose owners wouldn’t have to answer to a US Judge (the basic software is available now on many source websites for free under open-source licenses). Asking Apple to be the one source of software you know the gov’t can crack is like asking them to put themselves out of business for a single court case they aren’t a party to. Cook is right to say no and the government is clearly not thinking things through to even ask that Apple perform this task. Or, more likely, they’re just trying to score some political points.
To paraphrase the great Neil deGrasse Tyson, “Math is true whether or not you believe in it. That’s why it works.”