One person has been charged in connection with a large-scale fight at the La Mare playing fields, Guernsey Police said.
Another person has been formally cautioned after the "widespread disorderly behaviour".
Investigations are continuing after up to 200 people were involved in the disruption, which erupted on 8 May.
The force said it had also made 10 recommendations for referrals to the children's convenor.
In a statement on Twitter, Guernsey Police said: "While there are still interviews to complete, the investigation is now near its conclusion.
"We would again take this opportunity to ask parents to keep an eye on their children and ensure they are not getting involved in incidents similar to this one or other risk behaviours."
Police say they'll continue to monitor the issue of anti-social behaviour in Guernsey but are also urging parents to "keep an eye" on their children.