42 U.S. Code § 4654. Litigation expenses

(a) Judgment for owner or abandonment of proceedingsThe Federal court having jurisdiction of a proceeding instituted by a Federal agency to acquire real property by condemnation shall award the owner of any right, or title to, or interest in, such real property such sum as will in the opinion of the court reimburse such owner for his reasonable costs, disbursements, and expenses, including reasonable attorney, appraisal, and engineering fees, actually incurred because of the condemnation proceedings, if—
(1)
the final judgment is that the Federal agency cannot acquire the real property by condemnation; or
(2)
the proceeding is abandoned by the United States.
(b) Payment

Any award made pursuant to subsection (a) of this section shall be paid by the head of the Federal agency for whose benefit the condemnation proceedings was instituted.

(c) Claims against United States

The court rendering a judgment for the plaintiff in a proceeding brought under section 1346(a)(2) or 1491 of title 28, awarding compensation for the taking of property by a Federal agency, or the Attorney General effecting a settlement of any such proceeding, shall determine and award or allow to such plaintiff, as a part of such judgment or settlement, such sum as will in the opinion of the court or the Attorney General reimburse such plaintiff for his reasonable costs, disbursements, and expenses, including reasonable attorney, appraisal, and engineering fees, actually incurred because of such proceeding.

(Pub. L. 91–646, title III, § 304, Jan. 2, 1971, 84 Stat. 1906.)