Carl P Herslow, leader of the Skåne Party (Skånepartiet), a small right-wing populist regional party, is charged with agitation against an ethnic group (hets mot folkgrupp).
The poster included the text: 'He is 53 and she is nine. Is this the kind of wedding we want to see in Skåne?'.
Herslow admits producing the poster but contested the charges. He said the aim of the poster was to stimulate a debate about Islam, which he argued was incompatible with democracy and equality.
"The intention was to provoke a strong reaction among both Muslims and non-Muslims," he said.
Prosecutor Bo Birgerson, representing the Chancellor of Justice (Justitiekanslern - JK) - the country's top legal official, who is responsible for prosecution of cases involving freedom of speech - said that the distribution of the poster showed disrespect to Muslims.
Birgerson argued that previous cases in the Supreme Court showed that conviction for Herslow would not violate his right under Swedish law to freedom of speech.
"A conviction is important to show where the boundaries are for debate in an open and democratic society."
The prosecution argued that Herslow should to be given a suspended prison sentence and for the posters to be confiscated.
But after deliberating less than an hour the jury, which are only used in Sweden in freedom of speech cases, told the court that Herslow was not guilty of agitation against an ethnic group.
As a result, the court cannot convict the politician when it delivers its formal verdict on March 16th.