Criminal cases were launched following the festival last month.
Avon and Somerset Police officers say there's 'insufficient evidence' to continue their investigation into Kneecap.
However - they do continue to look into a second act - Bob Vylan.
Kneecap have posted a screenshot of an email - which appears to have come from police - informing the group and their representatives of the decision.
The group have criticised the decision to send it privately - despite the investigation being announced publicly.
They also say there's been no apology for what they described as 'media damage' and 'misleading headlines'.