The Metropolitan Police is investigating the "over zealous" actions of police community support officers (PCSOs).
The PCSOs confiscated alcohol from people having a picnic in Walpole Park in Ealing, west London, on 4 August.
It is not an offence to consume alcohol in the park but it is in a controlled drinking zone which means police have the power to stop people drinking.
The Met is looking into the details before deciding on what action to take.
A spokesman said: "While it is not an offence to consume alcohol within the designated area, the police have the power to stop people drinking and to confiscate alcohol.
"On this particular occasion it seems that the officers have acted in an over zealous manner enforcing the regulations of the controlled drinking zone."