Masimo Sues U.S. Customs Over Apple Watch Blood Oxygen Ruling

The Apple Watch blood oxygen saga isn’t over yet. Just a week after Apple re-enabled the feature on its latest U.S. models, Masimo has taken U.S. Customs and Border Protection (CBP) to federal court—claiming the agency unlawfully reversed course and gave Apple a free pass.

The Backstory

• October 2023: The International Trade Commission (ITC) ruled Apple infringed on Masimo’s patents related to pulse oximetry (blood oxygen monitoring).

• Result: Apple was forced to sell its newest Apple Watches in the U.S. with the feature disabled.

• The Biden administration declined to veto the import ban.

What Changed

In August 2025, CBP approved Apple’s new workaround: instead of calculating blood oxygen data directly on the watch, the final calculation happens on a paired iPhone. That update went live last week through iOS 18.6.1 and watchOS 11.6.1.

Masimo’s Complaint

Masimo argues CBP’s latest decision:

• Violated due process: The company wasn’t notified and only learned of the change after Apple’s announcement.

• Ignored prior rulings: CBP previously denied Apple’s “iPhone-based calculation” workaround in January 2025.

• Created a loophole: By refusing to consider indirect infringement, CBP allowed Apple to sell watches that still rely on the iPhone in the U.S. to complete the disputed function.

Masimo is now asking a federal judge to:

• Block the August ruling

• Reinforce the original ITC import ban

What’s Next

• Apple’s appeal of the ITC’s original ruling is still pending at the U.S. Court of Appeals.

• Meanwhile, Masimo’s case against CBP could determine whether Apple can keep offering blood oxygen on its watches in the U.S.

Takeaway: Apple may have found a clever workaround, but Masimo isn’t backing down. This case could set a big precedent for how U.S. agencies handle patent disputes—and for whether Apple Watch buyers get to keep one of its flagship health features.