He also said he recently became Muslim.
"This isn't cancel culture, this is a heartfelt plea from a place of genuine concern," writes fan Fiona Connor.
"The mass casualty events set off contagion events that can last for years."
Vague reports were received from members of the public - one of which "stated intention to undertake a school shooting", a counter-terrorism hui has been told.
"Ultimately, in a free society, people can spend their own money doing things like this."
I don't think we're ready to watch a movie about the attacks. Not now. Not ever, writes Mahvash Ali.
It was a big promise on a global stage but two years on, the effectiveness and transparency of the Christchurch Call is being called into question.
Ardern and French President Emmanuel Macron launched the Christchurch Call in the wake of the 2019 mosque shootings.
Here's what we know.