anti-gang
adjective
an·ti-gang ˌan-tē-ˈgaŋ 
ˌan-tī-
: opposed to gangs : designed to prohibit gangs or to prevent or punish criminal behavior by gang members
anti-gang laws
Following on the heels of recent weekend street gang sweeps by Los Angeles police, anti-gang units from the Sheriff's Department conducted their own operation last weekend, arresting 33 people on a variety of charges. 
The Los Angeles Times
The Los Angeles Times
Word History
First Known Use
1891, in the meaning defined above