A judge has backed Madrid's decision to force a bright orange bus emblazoned with an anti-transgender message off its roads.
Jose Juan Escalonilla said the bus could not move until the slogans, including "if you are born a man, you are a man", were removed.
The bus belongs to Catholic group, Hazte Oir, which had planned to take it on a nationwide tour of Spanish cities.
The public prosecutor is investigating whether it is a possible hate crime.
Other messages on the side of the bus state "boys have penises, girls have vulvas. Do not be fooled" and "if you are a woman, you will continue to be one".
Mr Escalonilla did not find the bus went as far as being a hate crime.
However, he said he believed the bus was an "act of contempt" meant to "injure" the dignity of people of a different sexual orientation, according to Spanish newspaper El Pais.
The bus is believed to be a response to posters put up in northern Spain by a transgender rights group, which read: "There are girls with penises and boys with vulvas. It's as simple as that."
'The bus of shame'
The vehicle was impounded after it was spotted in Madrid on Monday.
Though the outrage centres on its message, the bus has technically been ordered off the roads for breaching municipal rules on outdoor advertising.
Councilman for Security Javier Barbero said on Tuesday that police had halted "the bus of shame".
Ignacio Arsuaga, the president of Hazte Oir, which translates as "Make yourself heard", argued that the group had a right to protest against "laws of sexual indoctrination" and had the right to freedom of speech.
The group argued Madrid City Council's "kidnap" of the bus was "clearly illegal".
Mr Arsuaga claimed the slogan on the bus stated only "a fact of biology that is studied in schools".
The group told the BBC on Wednesday it was not expecting to meet so much opposition.
Mr Arsuaga said: "We are going to appeal this unjust decision and file a criminal case against the extreme-left Madrid mayor."
Hazte Oir intends to visit nine Spanish cities over two or three weeks, and is looking at getting a second bus.