PDF - http://fpc.state.gov/documents/organization/78335.pdf
Michael John Garcia
"Congress has broad plenary authority to determine classes of aliens who may be admitted into the United States and the grounds for which they may be removed. Pursuant to the Immigration and Nationality Act (INA),2 as amended, certain conduct may either disqualify an alien from entering the United States or provide grounds for his or her removal. Prominently included among this conduct is criminal activity."
