Dispersal orders have been imposed in Croydon town centre and Thornton Heath to prevent gangs of youths targeting shops.
Traders and residents in these areas are harassed by youths in large groups, damaging property and stealing from shops.
Police will now have the power to take youths under 16 to their homes if they could be victims or act anti-socially themselves.
The order will be in place until October 27.
Councillor Simon Hoar, Croydon cabinet member for community safety, said: "We will not tolerate this antisocial behaviour."
He claimed the order would help enforce law and make the community safer.
Inspector James Knowles, from Croydon Police, said retail stores support the order because anti-social behaviour affects their trade.
He said: "It is also distressing for the community, especially elderly residents, who fear large groups of youths."
The police assure those acting lawfully they will not be affected by the new orders which are punishable by three months in prison and/or a fine up to £2,500.