Three people have been arrested after hundreds of people gathered in Cardiff Bay on Friday.
Huge crowds were seen drinking and playing music outside the Senedd - despite Covid restrictions only allowing six people from two households to meet outside while maintaining social distancing.
South Wales Police said a 20-year-old man was arrested for a public order offence, a 22-year-old-woman was arrested for drunk and disorderly behaviour and possession of a Class A substance, and a 35-year-old man was arrested for possession of a Class A substance.
Officers said recent gatherings in the area have put additional pressure on the service and the local authority.
A Section 35 dispersal order has now been issued for the area, giving police officers the power to move people on.
Superintendent Marc Attwell said: "The practicalities of policing such large gatherings is incredibly difficult and we do still have emergency calls to attend.
"We are asking people in groups of six or more who are thinking of attending or organising a gathering down at the Senedd over this Bank Holiday weekend not to do so.
"Our officers will be out and about around Cardiff Bay throughout the Bank Holiday weekend. We’d urge people to be sensible and not to breach the rules – we don’t want anyone to be given a fine or be arrested for public order offences.
"As many restrictions are no longer in force, personal responsibility is critical if we are to prevent a third wave of infections. We all have a responsibility to make sensible choices when we are out and about, maintaining social distancing and not putting ourselves and others at unnecessary risk."
A clean-up operation got underway in the early hours of Saturday morning after large amounts of litter were left behind.
Industrial bins were installed in the area earlier this week, after litter was left behind following another gathering, but they were empty according to the council.
A large area surrounding the Senedd has been cordoned off and there is an increased police presence in Cardiff Bay.
A police CCTV van is also parked outside the building.