My last transaction was a Florida to Florida private sale. The seller proposed shipping it direct with no FFL, so I had to do some research and below is what I found out.
If he is an FFL, he can ship via USPS. If he is not, he cannot, period. USPS regulations also prohibit the mailing of a firearm to an individual by anyone.
From the Federal Firearms Laws:
Handguns 1.2
Pistols, revolvers, and other firearms capable of being concealed on the person (referred to as handguns) are non-mailable unless mailed between the parties listed in 1.3 and 1.5 after the filing of an affidavit or statement required by 1.4 and 1.6.
Authorized Persons 1.3
Subject to 1.4, handguns may be mailed by a licensed manufacturer of firearms, a licensed dealer of firearms, or an authorized agent of the federal government or the government of a state, territory, or district, only when addressed to a person in one of the following categories for use in the person's official duties:
a.Officers of the Army, Coast Guard, Air Force, Navy, Marine Corps, or Organized Reserve Corps.
b. Officers of the National Guard or militia of a state, territory, or district.
c. Officers of the United States or of a state, territory, or district, whose official duty is to serve warrants of arrest or commitment.
d. USPS employees authorized by the Chief Postal Inspector.
e. Officers and employees of enforcement agencies of the United States.
f.. Watchmen engaged in guarding the property of the United States, a state, territory, or district.
g. Purchasing agent or other designated member of agencies employing officers and employees included in 1.3c through 1.3e.
Affidavit of Addressee 1.4
Any person proposing to mail a handgun under 1.3 must file with the postmaster, at the time of mailing, an affidavit signed by the addressee setting forth that the addressee is qualified to receive the firearm under a particular category of 1.3a through 1.3g, and that the firearm is intended for the addressee's official use. The affidavit must also bear a certificate stating that the firearm is for the official duty use of the addressee, signed by one of the following, as appropriate:
a. For officers of Armed Forces, by the commanding officer.
b. For officers and employees of enforcement agencies, by the head of the
agency employing the addressee to perform the official duty with which the
firearm is to be used.
c. For watchmen, by the chief clerk of the department, bureau, or independent branch of the Government of the United States, the state, the territory, or the district by which the watchman is employed.
d. For the purchasing agent or other designated member of enforcement
agencies, by the head of such agency, that the firearm is to be used by an
officer or employee included in 1.3c through 1.3e.
Manufacturers and Dealers 1.5
Handguns may also be mailed between licensed manufacturers of firearms and licensed dealers of firearms in customary trade shipments, or for repairing or replacing parts.
From FEDEX terms and conditions:
FedEx Express will transport and deliver firearms as defined by the United States Gun Control Act of 1968, between areas served in the U.S., but only between:
Licensed importers; licensed manufacturers; licensed dealers; licensed collectors; law enforcement agencies of the U.S. or any department or agency thereof; and law enforcement agencies of any state or any department, agency or political subdivisions thereof; or
Where not prohibited by local, state and federal law, from individuals to licensed importers, licensed manufacturers or licensed dealers (and return of same).
If your shipment contains firearms, select the Direct Signature Required or Adult Signature Required Delivery Signature Option, depending on the requirements of your shipment. See the Delivery Signature Options section for details. Firearms shipments are not eligible for signature release or indirect delivery.
Firearms must be shipped via FedEx Priority Overnight service. FedEx Express cannot ship or deliver firearms C.O.D. Firearms shipments cannot be placed in a FedEx Express Drop Box.
Upon presenting the package for shipment, the person tendering the shipment to FedEx Express is required to notify FedEx Express that the package contains a firearm. The outside of the package must not be marked, labeled or otherwise identify that the package contains a firearm.
The shipper and recipient must be of legal age as identified by applicable law.
The shipper and recipient are required to comply with all applicable government regulations and laws, including those pertaining to labeling. The Bureau of Alcohol, Tobacco, Firearms and Explosives can provide assistance.
FedEx Express will transport ammunition when packed and labeled in compliance with local, state and federal law, and the Dangerous Goods section of this Service Guide. Ammunition is an explosive and must be shipped separately as dangerous goods. You agree not to ship loaded firearms or firearms with ammunition in the same package.
Item A, 2 is the key paragraph. It says FEDEX will allow shipment from a licensed dealer to an individual by stating "(and return of same)". One might argue that it clearly means returning a gun that has already been "booked" to an individual at some time and then was sent to a dealer for repair and returned. In other words, this does not allow circumventing the FFL recording and background check at some point for interstate deals. This is the way Colt, for example, returns guns directly. This is also the paragraph that allows an individual to send a gun to an FFL interstate or intrastate when you sell one.
Now, how about intrastate?
Well, no law prohibits individual to individual sales intrastate, at least in Florida. No law prohibits dealer to individual sales either, of course. However, according to FEDEX terms, an individual cannot ship to an individual. It seems also that technically a dealer could not ship to an individual either as part of a transfer, but that could be debated. However, doing so in either case would seem to be a violation only of FEDEX terms, not any federal or state gun laws.
Bottom line:
Individuals can neither legally ship nor receive guns via USPS. IMO an individual or a dealer could legally ship a gun being transferred to an individual intrastate in Florida, but both cases would seem to be a violation of FEDEX terms. What applies to FEDEX pretty much applies to UPS also. The risk in doing so is that at a minimum FEDEX (or UPS) would likely not honor any insurance claims in the event of loss or damage.
Since I am not a lawyer, this is JMO.