From my perspective, law enforcement of the drug business on the demand side would not be an effective method of reducing the market. As it was explained by Cook (2017), the criminal market is formed according to «net return per offense,» an analog of price, which increases accordingly to the desired quantity of offenses (p. 146). In the same study, Cook (2017) mentions that although a percent of criminals cease their illegal activity after completing rehabilitation programs, the net value of offense eventually creates another equilibrium and attracts new lawbreakers to the market (p. 147). In other words, after a presumable recovery or legal conviction of some drug users, the local market initially falls due to reduced demand but then draws new customers who get attracted by lower prices. It is important to keep in mind that drug-using is not a newly established issue; it has remained widespread for decades and is familiar to a major part of the public. With this in mind, I can conclude that the drug business works in a cyclical manner and cannot be terminated with demand-side actions only.
Regarding methods of controlling the drug business, I believe that emphasis on the suppliers is placed due to a lack of viable strategies for the other side. The most common mechanisms of implementing a criminal penalty for suppliers are searching their property and seizing the prohibited items (drug batches). However, when it comes to drug users, the prevalent methods are drug awareness campaigns and rehabilitation programs. While anti-drug campaigns might be effective for the impressionable audience, they hardly ever can influence more skeptical individuals or those who are already drug addicts. Rehabilitation, in its turn, has proven efficient for treating drug users and leading them to healthy lives, but it is a prolonged process, and it cannot be used massively. Given these points, it is evident that strategies for decreasing drug consumption are either weak in persuasion or narrowly targeted.
Reference
Cook, P. J. (2017). The demand and supply of criminal opportunities. In Natarajan, M. (Ed.), Crime Opportunity Theories (pp. 127-153). Routledge.