Proton's marketing definitely makes it sound like they are fully anonymous and wouldn't even have anything to hand over to law enforcement. Look at the wording they use to describe the product.

Proton has always-on end-to-end encryption and zero‑access encryption, meaning even we do not have access to your data.

[...]

Based in Europe, Proton ensures your data is protected by some of the world’s strongest privacy laws. Because Proton isn’t a US‑based company, we can’t be compelled by laws such as the US CLOUD Act to hand over your data to the US government or terminate your services. [1]

[1] https://proton.me/business/blog/proton-workspace

Obviously as we have seen, they 100% can and will hand over your data to the US government. Yes, it's in the privacy policy/ToS & they're compiling with local laws. But that's clearly not how that reads.

[In 2021, the Switzerland-based vendor provided local police with the IP address and device details of a netizen the cops were trying to identify. That individual – a French climate activist who was already known to police – was later arrested.

Shortly after that kerfuffle, Proton removed the claim that it didn't track user IP addresses from its website. Proton has also previously been accused of offering real-time surveillance of users to authorities.] [2]

[2] https://www.theregister.com/2024/05/13/infosec_in_brief/

See also: ProtonMail filters this into its junk folder: New claim it goes out of its way to help cops spy https://www.theregister.com/2019/05/29/protonmail_dismisses_...

A search on your favorite search engine of 'instances where proton has turned over user info to the government' will provide further reading.