No history of when you logged in from where and, possibly, plausible deniability about about you being the only user of that account (through you'd probably need to prepare for this to be believable).

I mean it's either this or traffic analysis. If you use your clearnet IP address to do illegal things, it's nothing more than reasonable that you can get in trouble for it.

This is also why I don't get protonmail in the first place. Unless you use pgp or equivalent, you'll always be subject to law enforcement. Just that protonmail cares more and caters more to activists and so might not give it out without checking that the asker is really legit and then give the minimal amount possible. But they'll always be able to turn over your emails and log IPs, it's not protonmail's fault the laws were voted into action like this.