Legal Question in Criminal Law in California

Re: Book / Media Mail Rate

They would probably not search any packages that were intact. The problem is if the package gets broken, and it becomes obvious that the package does not contain books, they might do somehting. I suspect this would be handled as a misdemeanor level crime, but in Federal Court. The cost to the Federal government would be prohibitive. You'd probably get to pay the difference in postage, and pay a small fine for a guilty plea; or my guess is as an alternative the postal service would contact you, and offer to drop the matter for the difference in the postage and payment of a small fee to cover their costs.

In any case the bother and worry would tell any intelligent person that the risk isn't worth it.