69-2403. Sale, lease, rental, and transfer; certificate required; exceptions.
(1) Except as provided in this section and section 69-2409, a person shall not purchase, lease, rent, or receive transfer of a handgun until he or she has obtained a certificate in accordance with section 69-2404. Except as provided in this section and section 69-2409, a person shall not sell, lease, rent, or transfer a handgun to a person who has not obtained a certificate.
(2) The certificate shall not be required if:
(a) The person acquiring the handgun is a licensed firearms dealer under federal law;
(b) The handgun is an antique handgun;
(c) The person acquiring the handgun is authorized to do so on behalf of a law enforcement agency;
(d) The transfer is a temporary transfer of a handgun and the transferee remains (i) in the line of sight of the transferor or (ii) within the premises of an established shooting facility;
(e) The transfer is between a person and his or her spouse, sibling, parent, child, aunt, uncle, niece, nephew, or grandparent;
(f) The person acquiring the handgun is a holder of a valid permit under the Concealed Handgun Permit Act; or
(g) The person acquiring the handgun is a peace officer as defined in section 69-2429.
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However..........................
NAC 272, Ch. 21 RECIPROCITY WITH OTHER STATES
004.01
Permits issued by other states or the District of Columbia to persons who are NOT residents of Nebraska will be recognized as valid in Nebraska if they are on the list maintained and published by the Nebraska Attorney General as jurisdictions issuing permits using standards which are equal to or greater than those in effect in Nebraska.
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However, this customer was a resident of Nebraska who had a permit from another state. So--it appears to this non-attorney that his out-of-state permit is NOT valid in Nebraska under this section.
Looks like you did the right thing in turning him down.