Factually incorrect...
As usual it actually pays to read carefully
and fully what the law and guidance actually say...
The
Guidance for U.S. Persons Traveling Outside the U.S. with Firearms and/or Ammunition that
318AE linked states:
Export regulations require that prior to traveling outside the United States with firearms and/or ammunition all departing persons must obtain a valid and appropriate DDTC or BIS export license
or qualify for a valid DDTC license exemption under
22 C.F.R. 123.17 - 123.18 or a valid BIS license exception under
15 C.F.R. 740.14(e).
Operating words: valid BIS license exception under 15 C.F.R. 740.14(e)
And here is what 15 C.F.R. 740.14(e) says (my highlights) about the Bureau of Industry and
Security (BIS) exception:
§ 740.14 Baggage (BAG)
(e) Special provisions for firearms and ammunition.
...
(3) A United States citizen or a permanent resident alien leaving the United States may export under this License Exception firearms, “parts,” “components,” “accessories,” or “attachments” controlled under ECCN 0A501 and ammunition controlled under ECCN 0A505.a,
subject to the following limitations:
(i) Not more than three firearms and 1,000 rounds of ammunition may be taken on any one trip.
(ii) “Parts,” “components,” “accessories,” and “attachments” exported pursuant to this paragraph (e)(3) must be of a kind and limited to quantities that are reasonable for the activities described in paragraph (e)(3)(iv) of this section or that are necessary for routine maintenance of the firearms being exported.
(iii) The commodities must be with the person's baggage.
(iv) The commodities must be for the person's exclusive use and not for resale or other transfer of ownership or control. Accordingly, except as provided in paragraph (e)(4) of this section, firearms, “parts,” “components,” “accessories,” “attachments,” and ammunition, may not be exported permanently under this License Exception. All firearms, “parts,” “components,” “accessories,” or “attachments” controlled under ECCN 0A501 and all unused ammunition controlled under ECCN 0A505.a exported under this License Exception must be returned to the United States.
(v) Travelers leaving the United States temporarily are required to declare the firearms, “parts,” “components,” “accessories,” “attachments,” and ammunition being exported under this License Exception to a Customs and Border Protection (CBP) officer prior to departure from the United States and present such items to the CBP officer for inspection, confirming that the authority for the export is License Exception BAG and that the exporter is compliant with its terms.
This is pretty clear cut, and t
he declaration and presentation to the CBP officer for inspection, and the issuance of a CBP Form 4457 fulfill the requirements of paragraph (V).