The bill before the state Legislature mirrors similar initiatives in Texas and Southern California and aims to curb drug dealing and violence on public property.
"These groups of kids that hang around together, that sell drugs, that run guns, if you're able to separate them, that's a huge benefit," said Boston Police Commissioner Edward Davis.
The anti-loitering law would ban groups of more than three gang members from being in parks and other declared "safe zones." It would not apply to school and church activities.
The Boston Globe said Wednesday that critics of the proposal see it as a violation of the civil rights of people who are not doing anything illegal or may have been mistakenly identified as gang members.
The Globe said individuals would be considered gang members based on court convictions and police intelligence.
The bill is currently before the Legislature's House Ways and Means Committee.