FedEx, UPS or USPS cooperation with drug detection programs where they detect drug shipments and then set up a sting. 

Assuming it went to the correct address usually the people who do this pick someone they know is usually not home so the package is left by the door. They then pick it up.

If it got left at the wrong house, well, welcome to happy, happy police state Amerika.  Your prior support for our brave, fearless policemen and the enforcement of our laws is expected to enthusiastically continue---understand?

Just as an aside, the article is wrong. When you place handcuffs on someone, THAT IS AN ARREST! Regardless of whether they were taken to jail or not, they still have been taken into custody.

 The only people who are surprised by this are those who aren't paying attention. Eventually, willful ignorance is going to get you.