37 U.S. Code § 462. Travel and transportation allowances paid to members that are unauthorized or in excess of authorized amounts: requirement for repayment

(a) Repayment Required.—
Except as provided in subsection (b), a member of the uniformed services or other person who is paid travel and transportation allowances under subchapter I shall repay to the United States any amount of such payment that is determined to be unauthorized or in excess of the applicable authorized amount.
(b) Exception.—
The regulations prescribed under section 464 of this title shall specify procedures for determining the circumstances under which an exception to repayment otherwise required by subsection (a) may be granted.
(c) Effect of Bankruptcy.—
An obligation to repay the United States under this section is, for all purposes, a debt owed the United States. A discharge in bankruptcy under title 11 does not discharge a person from such debt if the discharge order is entered less than five years after the date on which the debt was incurred.