Whoever harbors or conceals any person for whose arrest a warrant or process has been issued under the provisions of any law of the United States, so as to prevent his discovery and arrest, after notice or knowledge of the fact that a warrant or process has been issued for the apprehension of such person, shall be fined under this title or imprisoned not more than one year, or both; except that if the warrant or process issued on a charge of felony, or after conviction of such person of any offense, the punishment shall be a fine under this title, or imprisonment for not more than five years, or both.

Whoever willfully harbors or conceals any prisoner after his escape from the custody of the Attorney General or from a Federal penal or correctional institution, shall be imprisoned not more than three years.

Whoever moves or travels in interstate or foreign commerce with intent either (1) to avoid prosecution, or custody or confinement after conviction, under the laws of the place from which he flees, for a crime, or an attempt to commit a crime, punishable by death or which is a felony under the laws of the place from which the fugitive flees, or (2) to avoid giving testimony in any criminal proceedings in such place in which the commission of an offense punishable by death or which is a felony under the laws of such place, is charged, or (3) to avoid service of, or contempt proceedings for alleged disobedience of, lawful process requiring attendance and the giving of testimony or the production of documentary evidence before an agency of a State empowered by the law of such State to conduct investigations of alleged criminal activities, shall be fined under this title or imprisoned not more than five years, or both. For the purposes of clause (3) of this paragraph, the term “State” includes a State of the United States, the District of Columbia, and any commonwealth, territory, or possession of the United States.

Violations of this section may be prosecuted only in the Federal judicial district in which the original crime was alleged to have been committed, or in which the person was held in custody or confinement, or in which an avoidance of service of process or a contempt referred to in clause (3) of the first paragraph of this section is alleged to have been committed, and only upon formal approval in writing by the Attorney General, the Deputy Attorney General, the Associate Attorney General, or an Assistant Attorney General of the United States, which function of approving prosecutions may not be delegated.