Banning the biker gangs: Estimating the effects of civil bans on outlaw motorcycle gang members’ co-offending network

Abstract In an effort to combat cooperative criminal behavior by members of outlaw motorcycle gangs (OMCGs) Dutch law enforcement has successfully requested civil bans for six of the Netherlands most notorious OMCGs. While the civil bans are heralded as a triumph in the battle against OMCG crime, the effectiveness of these bans in disrupting co-offending among OMCG members has yet to be ascertained. In this study we use police registered co-offending data on 4,780 Dutch OMCG members to estimate the disruptive effect of the civil bans on Dutch OMCG members’ co-offending networks. To do so, we use nonparametric bootstrap hypothesis testing and sample 1,098 co-offending networks from the pre-ban period to gauge pre-ban co-offending network connectivity. Observed post-ban network connectivity is then compared to these bootstrapped mean values and confidence intervals to test whether the civil bans had a disruptive effect of OMCG members’ co-offending network. We find that compared to the co-offending networks distilled from the pre-civil ban period, the post-civil ban network was smaller, and more fragmented, suggesting a disruptive effect of the civil ban. Caveats to the data and analysis, and ramifications for policy are addressed.