Arbitrary criminalization through chemical equivalence: The misuse of GBL valuation as GHB in Spanish criminal law

This study critically examines the singular case of gamma-butyrolactone (GBL) in Spain—a substance that was initially controlled in 2002, together with GHB and its salts, esters, and ethers, under the national schedule of psychotropic substances. In 2006, after strong pressure from the Spanish chemical industry and following consultation with affected sectors, GBL and all esters and ethers of GHB were expressly removed from the national controlled substances list. The main justification was to prevent severe competitive disadvantages for Spanish industry, since GBL remained widely used as a chemical solvent, had no established therapeutic value, and was not subject to international or European criminal scheduling. Since then, GBL has not been subject to any criminal or administrative scheduling, and its trade is governed only by general chemical and commercial regulations—not by any special regime for controlled substances.

Paradoxically, while this 2006 legal reform effectively protected the interests of the chemical industry— removing both administrative and criminal controls over GBL for industrial operators—this exclusion has not been mirrored in the judicial-penal arena. Spanish criminal courts and forensic experts have continued to treat GBL as if it were gamma-hydroxybutyric acid (GHB), an internationally scheduled substance, justifying prosecutions under Article 368 of the Spanish Criminal Code. This legal fiction is operationalized through forensic valuations that equate GBL to GHB in both quantity and economic value, based on the well- established scientific fact that GBL is rapidly and completely converted to GHB in vivo. However, while this biochemical equivalence is undisputed, its legal application to justify criminal prosecution of GBL users— despite the substance’s explicit exclusion from controlled drug schedules—raises serious concerns regarding the principle of legality and proportionality in criminal law.

The research combines doctrinal legal analysis with an empirical review of more than one hundred court decisions (2006–2025), showing that these prosecutions rely on arbitrary and inconsistent methods, sometimes based on outdated or repealed regulations. Statistical modeling demonstrates a greater likelihood of conviction when GBL appears in chemsex contexts or among LGTBIQ+ defendants, indicating a pattern of indirect discrimination and stigmatization. This effect is especially pronounced in urban areas and among men who have sex with men, where the criminalization of GBL intersects with broader patterns of social stigma, targeted policing, and barriers to health and harm reduction services. The Spanish experience thus reflects not only a legal anomaly, but also the reproduction of structural vulnerabilities for sexual minorities in the context of emerging drug trends.

At the international level, both the United Nations and the International Narcotics Control Board (INCB) have explicitly recommended that the scheduling of GBL be decided at the national level, as it is not subject to international control. Regulatory approaches thus vary widely: some countries, such as the United States, the United Kingdom, and Latvia, have chosen to criminalize GBL directly, while others have imposed only administrative restrictions or precursor controls, and a few have shifted positions over time. Notably, GBL is not included in any official European Union schedules—neither as a psychotropic substance nor as a listed chemical precursor—further underscoring the singularity of Spain’s legal trajectory and the gap between industrial and criminal policy.