Here is just one example https://www.portland.gov/code/14/b90 https://www.portland.gov/code/14/b90 check out "14B.90.080 Reporting of Secondhand Dealer Transac

Here is just one example https://www.portland.gov/code/14/b90 https://www.portland.gov/code/14/b90 check out "14B.90.080 Reporting of Secondhand Dealer Transactions" details differ by state and city, but the gist is "electronic records of serials are transmitted to law enforcement" etc. Also items are held for a while, not sold immediately.