It is difficult to legally acquire fully automatic firearms at American gun shows (as opposed to the semiautomatic-only versions of these firearms that are legal on the U.S. civilian market), due to National Firearms Act (NFA). To legally purchase or transfer a fully automatic firearm, U.S. citizens must pay a $200 transfer tax, submit a full set of fingerprints on FBI Form FD-258, obtain certification provided by a chief law enforcement officer ("CLEO": the local chief of police, sheriff of the county, head of the State police, or State or local district attorney or prosecutor), and obtain final approval from the BATF on a Form 4 transfer of NFA registration to the new owner. All private citizens must wait, typically months, before receiving the tax stamp for the $200 tax paid, authorizing taking possession of the already paid-for fully automatic firearm. Until in receipt of the tax stamp, the Class III dealer retains control of the fully automatic firearm. In addition, only fully automatic firearms manufactured before the Firearm Owner's Protection Act of 1986 are permitted to be transferred. No fully automatic firearms recovered in Mexico have been traced to the United States.