New York State law.
a) General.
(1) The provisions of this section shall apply only in connection with the transportation, storage and sporting use of
black powder in quantities of five pounds or less when such powder is used in antique firearms or weapons or replicas thereof.
3)
A vehicle in transit carrying no other explosives than five pounds or less of black powder may be parked on a public street of a city, town or village near a dwelling, building or place where persons work, congregate or assemble provided that a designated person remains in such vehicle to guard the black powder.
39.12 Special provisions relating to black powder.
(a) General.
(1) The provisions of this section shall apply only in connection with the transportation, storage and sporting use of black powder in quantities of five pounds or less when such powder is used in antique firearms or weapons or replicas thereof.
(2) Persons shall use, store, buy, sell, possess, transport, receive or dispose of black powder only in accordance with the provisions of the Labor Law and of this Part (rule).
(b) Transportation.
(1) Vehicles carrying five pounds or less of black powder and carrying no other explosives shall be marked or placarded either on both sides or on both front and rear with circular signs or decals. Every such sign or decal shall have a minimum diameter of six inches and shall contain the letters "LOW-EX" in legible black letters at least one and one-quarter inches in height on a yellow background.
(2) A trailer may be attached to a vehicle carrying five pounds or less of black powder and carrying no other explosives. This paragraph does not modify the provisions of paragraph 39.11(g) (5) of this Part (rule) which prohibits the use of trailers for the transportation of explosives.
(3) A vehicle in transit carrying no other explosives than five pounds or less of black powder may be parked on a public street of a city, town or village near a dwelling, building or place where persons work, congregate or assemble provided that a designated person remains in such vehicle to guard the black powder.
(4) Passengers other than the driver may be permitted in any vehicle transporting five pounds or less of black powder and carrying no other explosives and provided the black powder is located in the trunk of the vehicle or otherwise separated from the passenger compartment.
(5) Smoking, if otherwise permitted by law, may be permitted by persons driving or riding in a vehicle containing five pounds or less of black powder and carrying no other explosives provided the black powder is located in the trunk of the vehicle or is otherwise separated from the passenger compartment. The other provisions of subdivision 39.11(c) of this Part (rule) shall remain in effect.
(6) Unloaded firearms may be permitted in a vehicle transporting five pounds or less of black powder and carrying no other explosives provided such firearms are securely fastened to a portion of the vehicle or located in a case or box and are separated from the black powder box.
(c) Storage. (1) Five pounds or less of black powder may be transported in a vehicle, stored in a residence other than a multiple dwelling or stored in a building other than a place of public assembly in accordance with the provisions of this paragraph.
(i) The black powder shall be either in the original shipping canisters, powder horns, powder flasks or as prepared charges in plastic or paper tubes.
Such containers shall be kept in locked boxes constructed of wood at least three-quarters inch nominal thickness. Handles shall be provided on each end or a single handle shall be centered on the top of each such box for quick removal in case of any emergency.
(ii) Each such box shall be painted red with the letters "LOWEX" at least one and one- quarter inches in height printed in yellow or white on the cover.
http://www.labor.state.ny.us/workerprotection/safetyhealth/sh39_12.shtm