Is ProtonMail legal in the US?

because ProtonMail is a Swiss company and stores all your data on servers in Swiss data centers, so ProtonMail is not bound by US law.

Protonmail FAQ Can the police track ProtonMail? Is ProtonMail more secure than Gmail? Does Protonmail work in China? Does ProtonMail hide IP addresses? Is ProtonMail a scammer? What is ProtonMail for? FAQ