Apple implemented a fix that turns off pulse oximetry when an Apple Watch is paired to an iPhone. Blood oxygen sensing becomes inaccessible to the user, and opening the blood oxygen app gives a warning that the feature is not available. Apple said that it hardcoded each Apple Watch at the factory with new software.
As part of the process to get approval to sell Apple Watch Series 9 and Ultra 2 models without pulse oximetry enabled, Apple had to provide the code disabling the feature and test devices to Masimo. Masimo didn't want Apple to have such an easy fix, so it paired the "redesigned" Apple Watches with a jailbroken iPhone running an older version of iOS, and was able to get pulse oximetry working.
Masimo tried to argue that activating pulse oximetry through a jailbroken phone meant Apple had not effectively removed the feature and the devices should not be allowed to be imported in to the U.S. Masimo also tried to say that jailbreaking is "permissible, common, and readily known,"
but Masimo's arguments were unsuccessful. The Exclusion Order Enforcement Branch of the
U.S. Customs and Border Patrol ultimately decided that disabling pulse oximetry in the Apple Watch Series 9 and Ultra 2 was enough to avoid infringing on Masimo patents, allowing those models to be offered for sale at Apple retail stores in the U.S.