Orin Kerr has written about the implications of that case specifically:<p><a href="https:&#x2F;&#x2F;www.washingtonpost.com&#x2F;news&#x2F;volokh-conspiracy&#x2F;wp&#x2F;2016&#x2F;02&#x2F;19&#x2F;preliminary-thoughts-on-the-apple-iphone-order-in-the-san-bernardino-case-part-2-the-all-writs-act&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.washingtonpost.com&#x2F;news&#x2F;volokh-conspiracy&#x2F;wp&#x2F;201...</a><p>A potentially important factor is that the phone companies used pen registers themselves all the time, whereas Apple has no desire at all to write the software that the FBI wants.<p>It&#x27;s worth noting that despite the outcome of that case, Congress still had to pass CALEA, which seems to imply there are limits to what can be compelled under All Writs.