Probably, but it would still be a huge win, if we could make it so they could only get e-mails with a normal warrant, from a normal Court (none of that secret courts/"millions of records-are-relevant nonsense).

Also, I don't know if it's currently "legal" or not to demand companies to keep encryption keys of what they're encrypting, but I'm pretty sure it's unconstitutional. So encrypting communications end to end should be constitutional/legal. The companies can still do that (if they have the will/customer pressure).

As for coerced backdoors, like they tried with Lavabit, that's just disgustingly immoral, and definitely unconstitutional.