Where restrictions on alcohol supply are less enforceable, however, such policies may not reduce alcohol-related harm at all. They may actually increase certain consequences as individuals put themselves at risk to procure alcohol in non-tribal jurisdictions (Gallaher et al., 1992; Landen, 1997; May, 1976).

Comparisons between tribes that prohibit alcohol and those that do not have suggested that alcohol-related consequences may actually be more prevalent in communities that prohibit alcohol (May, 1976), although this research does not support a causal interpretation because tribes that have retained prohibition may have done so as part of their response to higher levels of alcohol-related harm in their communities. Absent the kind of isolation that may permit local jurisdictions to effectively limit supply, prohibition may sometimes put individuals at risk as they try to procure alcohol at off-reservation sites (Landen, 1997; Gallagher et al., 1992). However, research in Alaska, where isolation may make local prohibition more effective, suggests that alcohol-related consequences are consistently lower in communities that prohibit alcohol (Berman, Hull, and May, 2000; Landen et al., 1997), and are further reduced in dry communities that also have a local police force (Wood and Gruenewald, 2006).