legal barriers to the operation of NEPs and other syringe access initiatives has been identified as an important part of a comprehensive approach to reducing HIV transmission among IDUs. Legal barriers include both "law on the books" and "law on the streets", i.e., the actual practices of law enforcement officers, which may or may not reflect relevant law. Changes in syringe and drug control policy can be ineffective in reducing such barriers if police continue to treat syringe possession as a crime or participation in NEP as evidence of criminal activity. Although most US NEPs operate legally, many report some form of police interference. In a 2009 national survey of 111 US NEP managers, 43% reported at least monthly client harassment, 31% at least monthly unauthorized confiscation of clients' syringes, 12% at least monthly client arrest en route to or from NEP and 26% uninvited police appearances at program sites at least every 6 months. In multivariate modeling, legal status of the program (operating legally vs illegally) and jurisdiction's syringe regulation environment were not associated with frequency of police interference. A detailed 2011 analysis of NEP client experiences in Los Angeles suggested that as many as 7% of clients report negative encounters with security officers in any given month. Given that syringes are not prohibited in the jurisdiction and their confiscation can only occur as part of an otherwise authorized arrest, almost 40% of those who reported syringe confiscation were not arrested. This raises concerns about extrajudicial confiscation of personal property. Approximately 25% of the encounters detailed by respondents involved private security personnel, rather than local police. Similar findings have emerged internationally. For example, despite instituting laws protecting syringe access and possession and adopting NEPs, IDUs and sex workers in Mexico's Northern Border regions report frequent syringe confiscation by law enforcement personnel. In this region as well as elsewhere, reports of syringe confiscation are correlated with increases in risky behaviors, such as groin injecting, public injection and utilization of pharmacies. These practices translate to risk for HIV and other blood-borne diseases. Racial gradient NEPs serving predominantly IDUs of color may be almost four times more likely to report frequent client arrest en route to or from the program and almost four times more likely to report unauthorized syringe confiscation. A 2005 study in Philadelphia found that African-Americans accessing the city's legally operated exchange decreased at more than twice the rate