Twelve people were arrested at an anti-lockdown protest in Wolverhampton.
West Midlands Police said it was made aware of 150 people gathering in the city on Saturday.
The force said it attempted to explain that protestors were in breach of ongoing restrictions, but “many did not listen” and refused to disperse.
It said its officers then “had to enforce the rules” and 12 people were taken into custody.
The force said it had information via social media that the protest was set to go ahead, and had earlier appealed for the organisers to make contact with officers.
But it said it received no contact before the gathering went ahead.
Some protestors went on social media to share images of the event, describing it as “peaceful”.
Since 5 November, people in England have been told to stay at home, and avoid meeting people they do not live with, except for in specific circumstances.
Supt Nick Rowe, from West Midlands Police said: “We always seek to speak with the people who are suspected of being in breach of the regulations, but when people are not working with us or listening to our instructions, then we must enforce the rules and arrest people where appropriate.”
It comes as the force said it had issued 155 fixed penalty notices and dispersed 179 people, with one person arrested, during the first week of the lockdown.