Two people were arrested during a protest outside the Labour Party Conference in Manchester.
Protesters gathered in Manchester city centre
They were part of an anti-nuclear demonstration which claimed it was refused permission to protest.
A Greater Manchester Police spokesman said a 62-year-old woman from Worsley, Greater Manchester, was cautioned for hitting a policewoman with a placard.
A 33-year-old man from Chorlton, Manchester, received a fixed penalty fine for a public order offence.
The Campaign for Nuclear Disarmament (CND), which said 100 people took part, said it had been prevented from unveiling banners which read: "No Trident replacement".
Police said there were 70 demonstrators.
A CND spokeswoman said the group was saddened that the protest had been prevented.
Kate Hudson, CND chairwoman, said: "It is a sad day for democratic debate and protest in Britain when we are prevented from raising nuclear weapons and war within the Labour Party conference and prevented from protesting about them outside."
Labour was criticised for not holding a debate at the conference on plans to upgrade Britain's Trident nuclear weapons system.
A Greater Manchester Police spokesman said: "Despite repeated attempts, protesters would not cooperate with police and therefore section 14 of the Public Order Act was imposed.
"The protesters were asked to remain in the Square, protest peacefully and then leave in pairs after 30 minutes."