Let's dispel one myth right now -- There is no statute of limitations on interstate trafficking of drugs:
Here's your link: Criminal Resource Manual 2186 Memorandum of Understanding -- Investigatory Authority and Procedures of Treasury and Justice Bureaus and the Postal Service Under 18 U.S.C. §1956 and 1957
This is a real threat to your freedom ladies and gents...be careful out there.
Legitimate domestic OLPs and foreign OLPs I know nothing about.