Under the red light settings, events and gatherings such as weddings are limited to 100 people, with vaccine passes, or 25 people if vaccine passes are not required.
The Prime Minister announced the wedding wouldn't go head during her press conference on Omicron on Sunday morning.
Ardern and Gayford, who have daughter Neve, were planning to get married this summer in Gisborne.
"When it comes to events, whether it's a birthday or a wedding or any kind of event of that nature, gathering limits of 100 do come in with the red light setting at 11.59pm tonight," Ardern said.
"It will depend on the nature of the event and if they are using vaccine passes - if they are not, it reduces to 25 people.
"As for mine, my wedding won't be going ahead but I just join many other New Zealanders who have had an experience like that as a result of the pandemic. And to anyone caught up in that scenario, I am so sorry, but we are all so resilient and I know we understand we are doing this for one another and it will help us carry on."
The PM was asked how she felt: "Such is life. I am no different to, dare I say, thousands of other New Zealanders."
Morgan has not always been against Ardern's measures when it comes to the pandemic.
In 2020, he went as far as saying he "wished" the UK had a leader like the New Zealand Prime Minister.