How would you bill the sender for this? The item is already in your local postal system by the time you know it is non-compliant. Itβs a choice between not delivering the packages, having the rest of the postal system subsidise them or ask the recipient to make up the difference.
IIRC, there is a way to do something similar in with the USPS, even if it is just a simple letter. Fill out a form, and the receiver gets a bill for the postage due. Something similar happens if you post a letter that cannot (for whatever reason) be returned: The receiver gets a bill they must pay before they can have the package.
I think that they figure the sender probably knows they are getting a lot of mail since the bulk of it is items ordered. They can know they are non-compliant by having standards on how many "free" packages one can receive and/or sending a notice when one is getting close to the limit.
Why are the people receiving the mail being billed extra when it is the sender failing compliance?
Shouldn't this be rolled into "shipping and handling" that the sender has to deal with?