37 USC 411i - Travel and transportation allowances: parking expenses

(a) Reimbursement Authority.— 
Under regulations prescribed by the Secretary of Defense, the Secretary of a military department may reimburse eligible Department of Defense personnel for expenses incurred after October 1, 2001, for parking a privately owned vehicle at a place of duty described in subsection (b).
(b) Eligibility.— 
A member of the Army, Navy, Air Force, or Marine Corps or an employee of the Department of Defense may be reimbursed under subsection (a) for parking expenses while
(1) assigned to duty as a recruiter for any of the armed forces;
(2) assigned to duty at a military entrance processing facility of the armed forces; or

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(3) detailed for instructional and administrative duties at any institution where a unit of the Senior Reserve Officers Training Corps is maintained.