A recent fight between two gang-affiliated groups fueled an uptick in shootings, officials said.
Police believe the victim was not the intended target of the Thursday afternoon shooting.
Enforcement of the new rule will begin July 7, police said.
Deputy Inspector George Fitzgibbon took over Crown Heights' 71st Precinct at the end of October.
Four children ranging in age from 10 to 14 were arrested in connection with alleged "knockout" attacks.
Investigators are still looking into whether the nine attacks are connected to the "knockout game."
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