That would mean, essentially, that they could not do anything at all with your packages unless they already have a reason to suspect you of a crime, and that even then, they have to have a reason to believe that a particular package is involved in said crime and even say beforehand what they expect to find in it.
Now, on to the specific scenario at hand. You might argue that that is too stringent, that no crime can ever be proven under that framework, and you may say it shouldn't preclude x rays and drug dogs and what not, I might even agree with you. But that as well as any other reasonable concept of justly handling suspicion precludes randomly opening peoples packages and keeping money by construing the simple presence of money as evidence that a crime maybe was committed and they get to keep it whether there was or wasn't a crime there. Even by the most lax framework of how to handle suspicion and searching property that is outrageous.