I'm not seeing that in the actual law now that I have read through it.
I did find these.
Federal Employees' Compensation Act
§8131. Subrogation of the United States
(a) If an injury or death for which compensation is payable under this subchapter is caused under circumstances creating a legal liability on a person other than the United States to pay damages, the Secretary of Labor may require the beneficiary to--
(1) assign to the United States any right of action he may have to enforce the liability or any right he may have to share in money or other property received in satisfaction of that liability; or
(2) prosecute the action in his own name.
An employee required to appear as a party or witness in the prosecution of such an action is in an active duty status while so engaged.
(b) A beneficiary who refuses to assign or prosecute an action in his own name when required by the Secretary is not entitled to compensation under this subchapter.
(c) The Secretary may prosecute or compromise a cause of action assigned to the United States. When the Secretary realizes on the cause of action, he shall deduct therefrom and place to the credit of the Employees' Compensation Fund the amount of compensation already paid to the beneficiary and the expense of realization or collection. Any surplus shall be paid to the beneficiary and credited on future payments of compensation payable for the same injury. However, the beneficiary is entitled to not less than one-fifth of the net amount of a settlement or recovery remaining after the expenses thereof have been deducted.
(d) If an injury or death for which compensation is payable under this subchapter is caused under circumstances creating a legal liability in the Panama Canal Company to pay damages under the law of a State, a territory or possession of the United States, the District of Columbia, or a foreign country, compensation is not payable until the individual entitled to compensation--
(1) releases to the Panama Canal Company any right of action he may have to enforce the liability of the Panama Canal Company; or
(2) assigns to the United States any right he may have to share in money or other property received in satisfaction of the liability of the Panama Canal Company.
§8132. Adjustment after recovery from a third person
If an injury or death for which compensation is payable under this subchapter is caused under circumstances creating a legal liability in a person other than the United States to pay damages, and a beneficiary entitled to compensation from the United States for that injury or death receives money or other property in satisfaction of that liability as the result of suit or settlement by him or in his behalf, the beneficiary, after deducting therefrom the costs of suit and a reasonable attorney's fee, shall refund to the United States the amount of compensation paid by the United States and credit any surplus on future payments of compensation payable to him for the same injury. No court, insurer, attorney, or other person shall pay or distribute to the beneficiary or his designee the proceeds of such suit or settlement without first satisfying or assuring satisfaction of the interest of the United States. The amount refunded to the United States shall be credited to the Employees' Compensation Fund. If compensation has not been paid to the beneficiary, he shall credit the money or property on compensation payable to him by the United States for the same injury. However, the beneficiary is entitled to retain, as a minimum, at least one-fifth of the net amount of the money or other property remaining after the expenses of a suit or settlement have been deducted; and in addition to this minimum and at the time of distribution, an amount equivalent to a reasonable attorney's fee proportionate to the refund to the United States.