Apple is fighting two high-stakes legal battles on opposite sides of the globe, challenging a US trade ban on its smartwatch health sensor and a massive EU antitrust fine.

Apple returned to the US Court of Appeals this week to contest a 2023 International Trade Commission ruling that forced it to remove the blood oxygen sensor from its Apple Watch.

The sensor, introduced with the Series 6 in 2020, was deemed to infringe patents held by medical tech firm Masimo.

Apple argues the ban was unjustified, claiming Masimo’s competing product was still hypothetical at the time and alleging Apple was unfairly penalised.

The ITC’s decision halted US imports of Apple Watch models with the sensor, prompting Apple to disable the feature via software in 2024 to resume sales.

The long-running dispute, which was rooted in Masimo’s 2020 accusations of trade secret theft and staff poaching, has seen both companies trade blows, with Masimo’s own smartwatch later found to infringe Apple patents.

Meanwhile in Europe, Apple is also appealing a €500 million (A$813 million) fine from the European Commission for violating the Digital Markets Act (DMA).

The EU found Apple’s App Store practices blocked developers from steering users to cheaper deals outside the platform, a breach the Commission said reflected the “gravity and duration” of Apple’s anti-competitive conduct.

Apple fired back, calling the fine “unprecedented” and accusing the EU of overreach.

“The EC is mandating how we run our store and forcing business terms which are confusing for developers and bad for users,” Apple said in a statement, as it filed its appeal with the EU’s General Court.