"I realised there was a problem about a month after we made a press release which said we had supplied some money to the Red Cross of North Korea who had used the money to buy PPE gear for the quarantine border service of North Korea," he told Morning Report.
"And our bank came to us asking us questions. Initially, they said they were just doing a routine audit of international transfers and started asking me questions. I asked them to put the questions in writing and it was clear there was more to it than met the eye."
Wilson said there was no way to send money directly to North Korea; 10 years ago it was possible "until the Americans stopped that".
So he found someone in Indonesia who they transferred the money to, who then passed on the cash to the North Korean embassy.
Alarm bells went off when the bank asked about the money trail to North Korea when all they should have known was the transfer to Indonesia, he said.
"To my surprise, I got an email which told me that they [the bank] had been alerted by the New Zealand Police... Can you believe it?
"And then they shut our bank account down. I thought that was the end of the matter. That all happened during July."
Only in October, he was met with police.
"But there's a knock on the door and I'm confronted by four policemen. They told me I was detained while they carried out a search of my house and they presented me with a search warrant which referred to the justified under United Nations Sanctions (Democratic People's Republic of Korea) Regulations 2017. For the next two hours they were here and they wanted post-2017 information.
"So I took them to the office, I told them everything that you want is in those boxes or on my laptop. They took my laptop and my cellphone."
Wilson was sure the money went to humanitarian efforts and said a receipt from the North Korean Red Cross and photos were evidence of it. They also put out that information in the press release.
"There's no secret about it. We're very proud that we're able to help them."
He said it was ironic that the police raided his house in the name of the UN.
"All of those UN sanctions specifically state they are not applicable to humanitarian aid.
"Although it's being done in the name of the UN all of this pressure on North Korea emanates from the policies of the United States. They have all been introduced to the security council by the US."
He has spent 50 years of his life as a humanitarian worker.
"While I was working professionally I spent all of my time working on projects in a wide range of countries in Asia and the Pacific, so I know that war is not the way to solve things. The only way to solve things is dialogue and working together with people.
"So I continue in retirement to be involved with North Korea because that's the biggest hotspot and really in my view the biggest ... problem area in the whole of our Pacific region."
The whole situation was painful, he said.
"I feel a bit upset that this has happened. I feel that it is totally needless and it is very inconvenient being deprived of my laptop and my cellphone."
But he said those would eventually be returned and it was nothing compared to the pain of the North Koreans who bore the brunt of the sanctions that often resulted in a shortage of food.
'This is a coordinated raid. It will have a name'
New Zealand-DPRK Friendship Society lawyer Matt Robson is demanding answers from the Government.
He doesn't accept the argument from Justice Minister Andrew Little and Police Minister Stuart Nash that the raids were an "operational" matter.
Robson told Morning Report the raid was "instigated by the Ministry of Foreign Affairs".
He said there was pressure on ASB Bank by the police to close the account much before the investigation was done.
Robson said the police was not equipped with data to carry out the search.
"You haven't got just the police. I've had a response from Stuart Nash saying it is an 'operational matter'. That's just nonsense and he'll know that."
And as for the search warrant - "I never got a signed copy."
While New Zealand authorities had a responsibility to step in if sanctions were breached, Robson said it was more in relation to weapons of mass destruction than PPE gear.
"This search warrant under [Search and] Surveillance Act can only be issued if there's imprisonment at stake. How can there be imprisonment at stake for what they've done, even if they've committed a technical breach, let's just say there is."
He said this was a "fishing expedition" and that several government departments and security authorities were involved.
"What they've got is people's names, addresses."
Basing his suspicion from his experience as associate minister of foreign affairs (responsible for official Overseas Development Aid [ODA]), where sanctions came up many times, Robson said the GSCB, SIS and MFAT were involved.
"This is a coordinated raid. It will have a name."
Robson also said the US had tried to "close down every agency that works in North Korea and they've done so successfully".
He said the New Zealand-DPRK Friendship Society had been involved in humanitarian efforts for many years.
"There is no breach of sanctions, this is humanitarian aid. PPE gear and everything else that the society has done is purely and clearly in the realm of humanitarian aid ... they are small amounts."
Police have been approached for comment.
