Italy's cabinet approved the vaccine law in mid-May, making it compulsory for all school starters to have a set of 12 vaccinations.
But in Veneto, the regional government said on Tuesday that its lawyers were preparing to challenge the decree in Italy's Constitutional Court, and that the legal challenge would be ready in around two weeks.
"Let's be clear; we are not against vaccines; we are against making them obligatory," explained regional governor Luca Zaia, who belongs to the Northern League.
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"Here, coverage was at 92.4 percent in 2016, thanks to information given to families at every level. No to sanctions, yes to informed decisions by mums and dads!"
Zaia wrote that it had been a "mistake to ignore the regions" in passing the legislation.
However, he appeared to acknowledge that fake news surrounding the efficacy and safety of vaccines had been an issue in Italy. "Fake news should be fought through science and doctors," he said.
The head of the Northern League, Matteo Salvini, praised the move in Veneto, writing: "Children's health comes before the interest of some pharmaceutical company [...] Freedom of choice works; threats and fines don't."
He also took the chance to push the party's anti-immigrant agenda, adding: "PS. Who vaccinates the illegal immigrants?"
Meanwhile, Liguria's regional vice-president and health councillor Sonia Viale said that the region would ask the government to amend the decree at the Conference of the Regions.
In particular, the Northern League politician wants the government to remove the clauses which mean parents who fail to get their child the necessary vaccines face fines, and the prospect of their child not being accepted into a state school.
"I say no to the imposition of vaccines when it impedes on parental rights," said Viale, according to Liguria Notizie.
And in Bolzano - a region where vaccination coverage is particularly low - there have been protests since the decree was passed. Around 130 families wrote to Italian President Sergio Mattarella to say they would "seek asylum" in Austria in order to avoid the mandatory vaccines, which they said infringed upon their human rights.
The regional council unanimously passed a motion calling for an end to "coercive measures" in favour of an awareness campaign
OPINION: 'Italy's mandatory vaccine law should be adopted worldwide'
Health Minister Beatrice Lorenzin. Photo: Emanuel Dunand/AFP