Protonmail has taken the perfectly reasonable position they will comply with the laws of the jurisdiction in which they are located: Switzerland. Other web mail services generally take the same position, though often in different jurisdictions. To the extent laws differ between Switzerland and the home countries of other services, they are different, and this would be true EVEN IF their technology, and policy for handling such requests, was identical to those of other web services.

From their privacy policy: https://protonmail.com/privacy-policy

We will only disclose the limited user data we possess if we are instructed to do so by a fully binding request coming from the competent Swiss authorities (legal obligation). While we may comply with electronically delivered notices (see exceptions below), the disclosed data can only be used in court after we have received an original copy of the court order by registered post or in person, and provide a formal response.

If a request is made for encrypted message content that ProtonMail does not possess the ability to decrypt, the fully encrypted message content may be turned over. If permitted by law, ProtonMail will always contact a user first before any data disclosure. Under Swiss law, it is obligatory to notify the target of a data request, although such notification may come from the authorities and not from the Company.

ProtonMail may from time to time, contest requests if there is a public interest in doing so. In such situations, the Company will not comply with the request until all legal or other remedies have been exhausted. Therefore, not all requests described in our Transparency Report will lead to data disclosure.