"Several bills introduced in the 109th Congress would make the unauthorized presence of aliens in the U.S. a criminal offense, including H.R. 4437, the Border Protection, Antiterrorism, and Illegal Immigration Control Act of 2005, introduced by Representative James Sensenbrenner on December 6, 2005 and passed by the House as amended on December 16, 2005, and S. 2454, the Securing America's Borders Act, introduced by Senator Bill Frist on March 16, 2006. The version of Chairman Arlen Specter's mark reported out of the Senate Judiciary Committee on March 27, 2006 does not contain a provision criminalizing unlawful presence, though the bill had initially contained such a provision. Although unlawful entry into the United States is both a criminal offense and a ground for removal, unlawful presence is only a ground for deportation and is not subject to criminal penalty, except when an alien is present in the United States after having been removed. This report briefly discusses some of the issues raised by criminalizing unlawful presence. Immigration law contains both civil and criminal provisions. The removal of aliens, however severe its consequences, has been 'consistently classified as a civil rather than a criminal procedure' by the courts. On the other hand, the Immigration and Nationality Act (INA) contains several provisions that are unambiguously penal in nature, subjecting offenders to imprisonment and/or fine under Title 18 of the U.S. Code."
CRS Report for Congress, RS22413