Federal requirements are that anyone purchasing a firearm from a licensed firearms dealer must complete a Bureau of Alcohol, Tobacco & Firearms firearms transaction form 4473. This form will be maintained by the dealer.
A firearms purchaser must, under the permanent provisions of the federal Brady law, also undergo a National Instant Criminal Background Check System (NICS) check which will be performed by the firearms dealer. The check will indicate to the dealer whether or not the purchaser's background allows for the person to actually complete the purchase of the firearm. If the check disallows the sale for no warranted reason, there is an appeals process which the purchaser can pursue to receive the necessary clearance to complete the purchase.
For questions regarding federal regulations please contact the Bureau of Alcohol, Tobacco and Firearms St. Paul, MN Regulatory Office at (651) 726-0220.
Additional information may be obtained from the Alcohol, Tobacco and Firearms publication Do I Need a License to Buy and Sell Firearms?