Police have seized 39 guns in a raid on a home in Pukekohe on Sunday morning, but the man who lives there says they have acted illegally.
The police say they went to the house at around 9am to serve a protection order on the man and to seize a number of firearms, NZME reports.
Insp Dave Glossop said the man refused to let police inside, so the armed offenders squad was deployed to assist in a "support role" alongside the negotiation team.
"Under section 18 of the Search and Surveillance Act, police gained peaceful entry to the address."
The act allows police to enter, search for and seize firearms without a warrant in the case of a protection order.
But the man, who is in his 50s, said no protection order was served and since his gate was locked, the police entry was unlawful.
A former police officer himself, he is now planning to file a complaint with the Independent Police Conduct Authority.
He told NZME police were at his house for more than four hours, and his family were terrified and in tears.
"My daughters were crying, my wife was crying. We were in lockdown in the bathroom.
"My mate rang to say, 'It's getting serious, they're putting bullet-proof vests on, there's the armed offenders squad and sledge hammers,'" he told NZME.
"I thought, 'I don't need to put my family through this'."
He began negotiating with police via text message, and eventually spoke with an officer and cooperated with police.
The man said the police took 39 guns from his two secure safes, including military-style rifles, pistols, and collectible items.