However, a person can be legally raided for the purposes of recovering said drugs, even if they have no idea that they possess them after picking the package up. Furthermore, even if the police has advance knowledge of the package and could have intercepted it earlier, they can still allow delivery and follow up with the raid, just so that they can take the recipient into custody. One prominent example:

https://en.wikipedia.org/wiki/Berwyn_Heights,_Maryland_mayor...