Wear only 1 of your uniforms when you are honorably discharged. All other uniforms and uniform parts remain the property of the armed forces. You may wear 1 uniform for the purpose of getting home. You must discontinue wearing the uniform after 3 months have passed from the date of your discharge.
BTW the punishment can be a fine or 6 month. The Marine Campaign Cover can only be worn by Drill instructors on active duty and then only with complete uniform.
7003. CAMPAIGN (SERVICE) HAT
1. The campaign hat may be worn with the duty uniform by Marines listed below, and is not authorized for leave, liberty, or in formation with troops, except as required for drill instructors. It will not be worn with the Blue Dress “A”/”B” uniforms. Service cap branch of service insignia will be worn in the center front ventilation eyelet. Hats, brims, chinstraps, and hat cords will be kept in a neat and serviceable condition. No deviation from the original shape and design of the hat is authorized.
a. Enlisted Marines. The hat is felt, Montana peak-type, with a 5-1/4-inch deep crown, 3-inch wide stiff brim, evenly formed, and thoroughly pressed. The hat is trimmed with a grosgrain ribbon and bow, has four round eyelets in the crown for ventilation and two oblong eyelets for leather chinstrap which is fitted with leather sliding keepers and a tongue-type center bar buckle.
b. Officers. To be identical to the enlisted hat except that the chinstrap is three-piece leather with a snap hook and fastener at two ends, and an adjustable tongue-type center bar buckle on the center piece. Officers will wear a scarlet and gold hat cord consisting of two rows of scarlet and gold cord held together by a sliding keeper, covered with scarlet and gold material of the same design as the cord. Each end of the cord projecting beyond the sliding keeper is finished with an acorn.
2. The hat is authorized for wear by the following personnel only:
a. At Recruit Depots/recruit rifle ranges when approved by the Commanding Generals.
(1) Assigned male and female drill instructors
(2) Sergeants major, recruit training regiments
(3) Recruit company first sergeants
(4) Primary marksmanship instructors conducting recruit marksmanship training
(5) Chief marksmanship instructors
(6) Line NCO’s and coaches
(7) Range officers (MOS 9925)
b. Drill instructors at Naval Aviation Officer Candidate School
c. Range officers (MOS 9925) at Marine Corps Combat Development Command, Quantico.
d. Members of the USMC rifle and pistol teams (Regular/Reserve) funded by HQMC.
Incorrect. The law and individual service codes allow for the uniform to be worn by all honorably and general discharged veterans on certain occasions such as funerals. All retirees may continue to wear. Officers retain all uniforms as they are their personal property.
Retired military members and certain honorably discharged veterans may wear the US Military uniform on certain occasions. This authority is authorized by Federal law (10 USC, 772). It allows certain veterans and retirees to wear the US Military uniform, as prescribed by the individual services.
In all cases, veterans and retirees can wear the rank and insignia currently in use, or the rank and insignia in use at the time of their discharge/retirement, but cannot mix the two.
The Navy Uniform Regulations prescribe the wear of the Navy uniform by Navy retirees and veterans.
Army Regulation 670-1 prescribes uniform wear by Army veterans and retirees.
The Marine Corps Uniform Regulation, MCO P1020.34G prescribes wear of the Marine Corps uniform by retirees and veterans.
In addition a veteran may be eligible to retain their title: 10 U.S.C. Sec. 772: When wearing by persons not on active duty authorized.
(e) A person not on active duty who served honorably in time of war in the Army, Navy, Air Force, or Marine Corps may bear the title, and, when authorized by regulations prescribed by the President, wear the uniform, of the highest grade held by him during that war.
You can call me Lieutenant, USN ;) (I had to dig all this up for a funeral a few years back.)