I found the answer at
http://immigration.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%2Ftravel.state.gov%2Fvisa%3Bineligible.html and have copy & pasted the secton that applies below. I hope this helps.
Classes of Aliens Ineligible to Receive Visas
The following sections of the law are taken from the immigration and Nationality Act, 8 U.S.C. 1001, et. seq., as amended by Public Law 101-549 of November 29, 1990.
Section 212 (a) of the Immigration and Nationality Act reads as follows:
Classes of Excludable Aliens - Except as otherwise provided in this Act, the following describes classes of excludable aliens who are ineligible to receive visas and who shall be exclude from admission into the United states.
(2) CRIMINAL AND RELATED GROUNDS.--
(A) CONVICTION OF CERTAIN CRIMES.--
(i) IN GENERAL.-- Except as provided in a clause (ii), any alien convicted of, or who admits having committed, or who admits acts which constitute the essential elements of--
(I) a crime involving moral turpitude (other than a purely political offense), or
(II) a violation of (or a conspiracy to violate) any law or regulation of a State, the United States, or a foreign country relating to a controlled substance (as defined in section 102 of the Controlled Substances Act (21 U.S.C. 802)), is excludable.
(ii) EXCEPTION.-- clause (i)(I) shall not apply to an alien who committed only one crime if--
(I) the crime was committed when the alien was under 18 years of age and the crime was committed (and the alien released from any confinement to a prison or correctional institution imposed for the crime) more than 5 years before the date of application for visas or other documentation and the date of application for admission to the United States, or
(II) the maximum penalty possible for the crime of which the alien was convicted (or which the alien admits having committed or of which the acts that the alien admits having committed constituted the essential elements) did not exceed imprisonment for one year and, the alien was not sentenced to a term of imprisonment in excess of 6 months (regardless of the extent to which the sentence was ultimately executed).
(B) MULTIPLE CRIMINAL CONVICTIONS.-- Any alien convicted of 2 or more offenses (other than purely political offenses), regardless of whether the conviction was in a single trial or whether the offenses arose from a single scheme of misconduct and regardless of whether the offenses involved moral turpitude, for which the aggregate sentences to confinement actually imposed were 5 years or more is excludable.
(D) PROSTITUTION AND COMMERCIALIZED VICE.-- Any alien who--
(i) is coming to the United States solely, principally, or incidentally to engage in prostitution, or has engaged in prostitution within 10 years of the date of application for a visa, entry, or adjustment of status,
(ii) directly or indirectly procures or attempts to procure, or (within 10 years of the date of application for a visa, entry, or adjustment of status)
procured or attempted to procure or to import, prostitutes or persons for the purpose of prostitution, or receives or (within such 10-year period) received, in whole or in part, the proceeds of prostitution, or
(iii) is coming to the United States to engage in any other unlawful commercialized vice whether or not related to prostitution, is excludable.
(E) CERTAIN ALIENS INVOLVED IN SERIOUS CRIMINAL ACTIVITY WHO HAVE ASSERTED IMMUNITY FROM PROSECUTION.--Any alien--
(i) who has committed in the United States at any time a serious criminal offense (as defined in section 101(h)),
(ii) for whom immunity from criminal jurisdiction was exercised with respect to that offense,
(iii) who as a consequence of the offense and exercise of immunity has departed from the United States, and
(iv) who has not subsequently submitted fully to the jurisdiction of the court in the United States having jurisdiction with respect to that offense, is excludable.
(F) WAIVER AUTHORIZED.-- For provisions authorizing waiver of certain subparagraphs of this paragraph, see subsection (h).
