The Federal Analog Act, 21 U.S.C. § 813, is a section of the United States Controlled Substances Act, allowing any chemical "substantially similar" to an illegal drug (in Schedule I or II) to be treated as if it were also in Schedule I or II, but only if it is intended (ref 1) for human consumption. The banned substances are often called designer drugs or research chemicals.
The LawThe term “controlled substance analogue” is defined as a substance:
(i) the chemical structure of which is substantially similar to the chemical structure of a controlled substance in schedule I or II;
(ii) which has a stimulant, depressant, or hallucinogenic effect on the central nervous system that is substantially similar to, or greater than, the stimulant, depressant, or hallucinogenic effect on the central nervous system of a controlled substance in schedule I or II; or
(iii) with respect to a particular person, which such person represents or intends to have a stimulant, depressant, or hallucinogenic effect on the central nervous system that is substantially similar to or greater than the stimulant, depressant, or hallucinogenic effect on the central nervous system of a controlled substance in schedule I or II.
Explanation of the LawFor a substance to be considered an analog under the US Federal Analogue Act, it seems two of three conditions must be met.
The chemical must be 1. 'substantially similar'
2. have effects similar to substance in Schedule I or II
3. someone represents it as having the effect of a controlled substance (ref 2)
Exemptions from the Analog ActAs enacted, the federal Controlled Substance Analogue Act provides four express exemptions.
Under the act, the term “controlled substance analogue” does not include:1. A controlled substance
2. Any substance for which there is an approved new drug application
3. With respect to a particular person any substance, if an exemption is in effect for investigational use, for that person, under section 505 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 355) to the extent conduct with respect to such substance is pursuant to such exemption
4. Any substance not intended for human consumption before such an exemption takes effect, with respect to that substance.
Jurisdiction of Analog ActThe Federal Analogy Act only covers the USA and it's territories. However other countries have similar laws. One should be aware of the laws that govern whatever country they live in or decide to travel to.
Known Legal CasesA DEA operation, "Operation Web Tryp" ending with 10 arrests on July 21, 2004. Relating to phenethylamines/typtamines that are not explicitly scheduled sold, on the internet.
USA v. Damon S. Forbes (1992) - AET is determined not to be an analog of DET and DMT
USA v Washam (2002) - 1,4-butanediol is ruled to be an an analog of GBH.
Operation Log Jam
On July 25 2012, members of the DEA and the US Immigration and Customs Enforcement Bureau along with numerous other state and local agencies conducted nationwide raids against US based research chemical suppliers, manufacturers and vendors. All told, 90 individuals were arrested and 19 million packets of synthetically produced drugs were seized. 36 million dollars in cash was also confiscated. Synthetic cannabinoids (ex. K2, Spice)and synthetic cathinones (i.e. "bath salts") were seized and the DEA plans to charge and prosecute their producers and vendors under the Controlled Substance Analogue Enforcement Act of 1986 (AEA). It was the largest ever operation targeted solely on research chemicals. 
John E Tebbetts ‘, owner of Tebb’s tobacco stores ranging from New York State to Maine on the North east coast of the US. Tebb’s stores and warehouse were raided on July 25th and 26th . Agents seized $1 million worth of synthetic drugs; $400,000 in cash; a 2012 $300,000 RV; seven other vehicles, including a custom-painted Tebb’s Head shop vehicle and a Cadillac; 33 pounds of unpackaged synthetic marijuana; 70,000 foil packets of synthetic marijuana; and 50,000 packets of bath salts.
Mr. Tebbetts’ was brought up on three counts of each: possessing a controlled substance analog : a drug that is chemically similar to a controlled substance : with the intent to sell the drugs at his head shops. Tebbetts’ subsequently pleaded guilty all charges, agreeing to forfeit $314,000 in cash and six vehicles.
Under federal sentencing guidelines, Mr. Tebbetts’ should face 13-16 years in prison, but it is speculated to be closer to 6-8 years in prison his sentencing date is scheduled for April 29th 2012.
History of Federal Analog ActThe Federal Analog Act was added to the The Control Stubstances Act in 1986.
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