Police in Dordrecht wrongfully arrested two men on an anti-Zwarte Piet demonstration during a Sinterklaas parade in 2011, the national ombudsman ruled on Friday.

The men, who were wearing t-shirts with the slogan ‘Zwarte Piet is racism’, were arrested for disturbing the peace after parents called on police to take action. The ombudsman ruled their arrest was unlawful, disproportionately violent and a violation of their human rights

The arrest of artist Quinsy Gario and rapper Cesare Kno’ledge marked the start of a nationwide debate about the link between Sinterklaas’ sidekick and slavery.

The fact that skin colour played a part in the arrest became clear from the questions the protesters were asked by the police.

‘What is your background that you want to draw attention to this?’ was one question and ‘Don’t you see Sinterklaas as a tradition?’, was another. The ombudsman judged the interrogating officer’s  questions to be ‘unprofessional’, the NRC said.

The public prosecution department had already dropped charges against the men in 2012.