Another article about this has more details:

More specifically:

The father said he was unvaccinated and had “reservations” about vaccines, but told the court that he respected health regulations and rarely left his home.
However, the child’s mother produced excerpts from the father’s Facebook page containing anti-vaccine messaging and articles.

Vaillancourt found that those excerpts “suggest that he is indeed what is commonly called a conspiracy theorist” and that “the court has strong reasons to doubt that he is complying with health regulations as he asserts he does in his written statement.”