"We found that the odds of being arrested or cited for drug paraphernalia in a 6-month period were significantly higher for clients of legal SEPs [syringe exchange programs] when compared to clients of illegal SEPs. Although both illegal and legal SEPs operate in neighborhoods with heavy drug use and drug sales, policing strategies may be heavily concentrated around the known presence of a legal SEP. Illegal SEPs may operate in more hidden venues or use program methods, such as syringe exchange delivery and satellite exchange models to reduce or eliminate exposure to law enforcement."

Source

Martinez, A. N., Bluthenthal, R. N., Lorvick, J., Anderson, R., Flynn, N., & Kral, A. H. (2007). The impact of legalizing syringe exchange programs on arrests among injection drug users in California. Journal of urban health : bulletin of the New York Academy of Medicine, 84(3), 423–435. doi.org/10.1007/s11524-006-9139-1