Sure. But I'm not worried about someone who has an actual warrant for ME getting at stuff.
What I want to stop is some random law enforcement idiot from Dipshitsville, Texas, from sending an electronic request to Google for "every email with the word "abortion" and "protest" in it" who promptly turns over all my email.
If you want my email, you're gonna have to get up off your chair, file a warrant with somebody's name on it in front of a judge, crossfile in some different legal jurisdictions, and have someone come seize my machines.
That will stop most everybody short of NSA.
If your threat is the NSA, you're screwed anyway. If they can't get at your email legitimately, they'll just fabricate the evidence they need against you.
The NSA doesn’t need evidence; you must have them confused with the FBI.
Self-hosting at least means that this should not apply, I think.