Update 01/18/24: The appeals court has denied Apple’s motion (PDF) for a continuing stay on the sales ban, which means that the ban is back in effect beginning January 18 at 5 pm. ET. To continue selling the watch, Apple has removed the blood-oxygen sensor’s functionality while the case works its way through the courts.

Following the dramatic news in December that its flagship Apple Watch Series 9 and Ultra 2 smartwatches were being banned from sale, Apple has been hustling ever since to get them back on the market and keep them there. The problem is that the ITC has ruled that blood-oxygen sensors in the devices infringe patents owned by another company named Masimo.

The initial ban lasted only a few days, with an appeals court granting Apple’s request for a temporary stay, but the future remains uncertain. The company wants the ban to be paused for the entire appeals process, which could last a year or more and comfortably take us through to the launch of the next generation of Apple Watches, but the ITC for one finds Apple’s arguments for this course of action “weak and unconvincing” and success is by no means assured.

Last month it began work on a software workaround for the offending smartwatches, saying this would resolve the patent dispute to all parties’ satisfaction, and this week it emerged that US Customs has given its approval. We’ve also learned more about the workaround itself, and it turns out the changes are far more drastic than previously suspected. Rather than tweaking or even redesigning the process by which the watches measure blood oxygen, the software update removes the feature entirely. Obviously, Apple isn’t going to physically remove the sensor from the device, but it’s disabled for this purpose at least by a software inhibition. This was revealed by Masimo (as reported by Bloomberg), with whom the customs agency shared its findings.

“Apple’s claim that its redesigned watch does not contain pulse oximetry is a positive step toward accountability,” the company commented. “It is especially important that one of the world’s largest and most powerful companies respects the intellectual property rights of smaller companies and complies with ITC orders when it is caught infringing.”

Fear not, the firmware update does not apply to any watch shipped before January 18. If you have a Series 9 or any older Apple Watch with a blood-oxygen sensor, it will work as it should. To check whether your watch has the sensor enabled, head to the General tab in the Settings app, then About and Model, and tap to see the Part Number. Watches that have the blood oxygen sensor disabled have part numbers that end with the letters LW/A while working models end with LL/A.

The oxygen saturation (SpO2) sensor arrived with the Apple Watch Series 6 and takes on‑demand readings of your blood-oxygen levels as well as background readings throughout the day and night. Apple stresses that it’s for “wellness purposes only,” but the feature has been credited with saving lives.