N.P.
it doesn't matter if it's illegal or not, it's how you feel about it. If it bothers you, ask yourself why it does. My husband goes on my facebook and email accounts all the time and reads my stuff. I don't care cause I have nothing to hide from him. We share every detail of our lives for the most part so it doesn't bother me at all. No, he doesn't control me, but we have no secrets cause we are married.
If it bothers you, set up a new email password and make it something unbreakable, clear your cookies after you use the computer and be secretive. OR talk to him about it and ask him to not do it and explain why. OR go to marriage counseling cause it sounds like there might be trust issues. I mean to ask if it's illegal means you would have him charged with a crime. Your husband? Hmm...