http://www.law.cornell.edu/uscode/html/uscode0 8/usc_sec_08_00001182----000-.html
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 a visa 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, if the alien was convicted of such crime, 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 were 5 years or more is inadmissible.
(C) Controlled substance traffickers
Any alien who the consular officer or the Attorney General knows or has reason to believe�
(i) is or has been an illicit trafficker in any controlled substance or in any listed chemical (as defined in section 802 of title 21), or is or has been a knowing aider, abettor, assister, conspirator, or colluder with others in the illicit trafficking in any such controlled or listed substance or ch