Though Congress has thus no power to limit in any way the exercise of the pardoning power by the President, it may itself exercise that power to a certain extent, if exercised prior to conviction. Thus acts of amnesty have been held valid. In Brown v. Walker39 the act of Congress granting immunity from prosecution to witnesses testifying before the Interstate Commerce Commission was upheld, the court saying: "Although the Constitution vests in the President power to grant reprieves and pardons for offenses against the United States, except in cases of impeachment, this power has never been held to take from Congress the power to pass acts of general amnesty."

In Pollock v. Bridgeport S. B. Co.40 it was held that the pardoning power of the President was not so exclusive as to prevent other officers, acting in conformity with statute, from remitting forfeitures and penalties incurred for the violation of laws of the United States. In its opinion the court say:

"It is not necessary to question the soundness of some of these propositions. It may be conceded that, except in cases of impeachment and where fines are imposed by a coordinate department of the government for contempt of its authority, the President, under the general qualified grant of power to pardon offenses against the United States, may remit fines, penalties and forfeitures of every description arising under the laws of Congress; and, equally, that his constitutional power in these respects cannot be interrupted, abridged or limited by any legislative enactment. But is that power exclusive, in the sense that no other officer can remit forfeitures or penalties incurred for the violation of the laws of the United States ? This question cannot be answered in the affirmative without adjudging that the practice in reference to remissions by the Secretary of the Treasury and other officers, which has been observed and acquiesced in for nearly a century, is forbidden by the Constitution. That practice commenced very shortly after the adoption of that instrument, and was perhaps suggested by legislation in England, which, without interfering with, abridging or restricting the power of pardon belonging to the Crown, invested certain subordinate officers with authority to remit penalties and forfeitures arising from violations of the revenue and customs laws of that country."

39 161 U. S. 591; 16 Sup. Ct. Rep. 644; 40 L. ed. 819. 40 114 U. S. 411; 5 Sup. Ct. Rep. 881; 29 L. ed. 147.