Legal Question in Criminal Law in California

First, not a bright idea. I believe it is not illegal but I bet they assume it was being mailed for illegal purposes, otherwise you would have sent by secure means. You know it was intercepted, I bet they sent you a way to claim it... If the transaction or reason was illegal it will incriminate you. If you were mailing it outside the US there are other issues like declarations that should have been filed.

What should you do?

First learn some good sense about risking cash in the mail, from theft, etc.

Then learn the laws on money transfer or criminal conspiracy crimes which you are at risk of facing. That's why they seized it.

Then formally demand in writing the return of the seized funds, followed up with a lawsuit if refused.

More to the point however, is that you should get ready with an attorney to represent you in the seizure and the possible criminal charges.

If serious about hiring counsel to help in this, and if this is in SoCal courts, feel free to contact me. I�ll be happy to help fight and get the best outcome possible.