Apple Watch oxygen workaround triggers new lawsuit from Masimo
Apple’s latest software update for the Apple Watch brought back blood oxygen tracking in the US, but not without controversy. Masimo is now suing US Customs, arguing the government agency had no authority to let Apple re-enable the feature in this way.
Masimo takes aim at Apple’s latest SpO2 workaround
Masimo has filed a new lawsuit, but this time Apple isn’t the direct target. Instead, the medical device company is going after the US Customs and Border Protection agency. The legal move comes just days after Apple reintroduced blood oxygen functionality to newer Apple Watches sold in the United States via a software update.
The update, which arrived as part of watchOS 11.6.1 and iOS 18.6.1, enables SpO2 readings for Series 9, Series 10 and Ultra 2 models purchased after January 17, 2024. These watches originally shipped with the sensor disabled due to an ongoing patent dispute between Apple and Masimo. That dispute had led to an import ban late last year, which Apple complied with by selling affected models with the feature disabled.
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Apple’s workaround from a few days ago involves shifting the data processing to the iPhone. Users can now see their blood oxygen readings in the Health app under the Respiratory section, but not on the watch itself. This shift, likely crafted with legal precision, is what Masimo now challenges.
The heart of the new lawsuit
According to court filings, Masimo believes US Customs unlawfully changed its stance on the matter. The agency had previously blocked imports of Apple Watches with blood oxygen functionality enabled. But on August 1, 2025, it reversed that position, giving Apple the green light to roll out its redesigned feature.
Strangely enough, Masimo claims it had no knowledge of this reversal until Apple made its announcement on August 14. The company describes Customs’ approval as an “ex parte ruling,” meaning Masimo was not informed or allowed to weigh in before the decision was made.
“It has now come to light that CBP thereafter reversed itself without any meaningful justification, without any material change in circumstances, and without any notice to Masimo, let alone an opportunity for Masimo to be heard. CBP changed its position on Apple’s watch-plus-iPhone redesign through an ex parte proceeding. Specifically, on August 1, 2025, CBP issued an 3 ex parte ruling permitting Apple to import devices that, when used with iPhones already in the United States, perform the same functionality that the ITC found to infringe Masimo’s patents. Masimo only discovered this ruling on Thursday, August 14, 2025, when Apple publicly announced it would be reintroducing the pulse oximetry functionality through a software update.”
Masimo argues that the redesigned system, where the watch collects data and the iPhone processes it, still infringes on the same patents that triggered the original exclusion order. In its court filing, the company said the move “effectively nullified” the earlier ban issued by the US International Trade Commission.
They are now asking the court for a temporary restraining order and a preliminary injunction that would block the CBP decision and reinstate the prior enforcement terms. Their appeal rests heavily on the idea that Apple’s feature, even with the redesign, still achieves the same outcome and thus continues to violate Masimo’s intellectual property.
Where this could go next
This latest legal move adds more friction to an already drawn-out dispute. Apple’s appeal of the original ITC ruling is still pending in the Federal Circuit. Masimo is now working both ends, challenging the broader decision through that channel while also trying to reverse Customs’ more recent green light.
For users in the US, this may not immediately change anything. The blood oxygen functionality, while not back to the way it worked before, is at least usable again for now. However, if Masimo’s request for a restraining order is granted, Apple could once again be forced to disable the feature.
So if you’re using it, don’t count on it sticking around. Oh, and you might want to switch auto-updates to off!
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