Legal Question in Real Estate Law in California

Once mail is delivered to address, the postal service has no further interest in what happens to it; its job is complete, and there is no possibility of a crime related to interference with transportation or delivery of the mail (see definition of mail theft in 18 USC 1708). Similarly, I can find no law criminalizing members of the same household, living at the same address, from opening heach other's mail. This is not to say that opening someone else's mail at your address could not be part of some other crime, such as theft of money, checks, etc. in the envelope. The mere act of opening an envelope and looking at the contents does not seem to be a crime; at most, maybe a tort.