Criminal Defense of Immigrants
§ 21.15 (B)
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(B) Drug Addiction. Drug addiction is defined by regulation to include the non-medical use of a controlled substance “which has resulted in physical or psychological dependence.”  Drug addict is further defined under 42 U.S.C. § 201(k) as a person who has “lost the power of self control” over his or her addiction, or whose habitual drug use poses a threat to public morals, health, safety, or welfare. A “mere user” is not an addict.
 42 C.F.R. § 34.2(h) (as amended by May 31, 1991 interim rules, 56 Fed. Reg. 25000), reported on and reproduced in Interpreter Releases (June 3, 1991 and June 17, 1991).
 See Matter of KCB, 6 I. & N. Dec. 374 (BIA 1954), holding that conviction under what is now California Health & Safety Code § 11550 (use or under the influence) does not necessarily show addiction.
CONTROLLED SUBSTANCES - DRUG ABUSE AND ADDICTION
USCIS released a new medical examination form, dated 04/02/08, which includes specific questions on controlled substance use and addiction (Part 2, Q. 4), and has detailed instructions to physicians about completing these questions (page 6). Counsel must therefore prepare clients for medical exams and interviews by asking, "Have you ever smoked marijuana?" and "Are you in remission? Because if you are not in remission, you are inadmissible and have no waiver (unless you are a refugee or asylee doing AOS)." The HHS guidelines provide that an addict is someone who uses or has used a controlled substance for more than a single, experimental use. I-693 instructions: http://www.uscis.gov/files/form/I-693instr.pdf
Thanks to Deborah S. Smith.