The society has been scrutinising the separation-international.com website since it emerged it was registered to Mr Guest's brother, Auckland lawyer Andrew Guest, but to Michael Guest's Dunedin address, phone number and email address.
Mr Guest, a former district court judge and also a Dunedin city councillor, was struck off for professional misconduct in 2001.
He was reinstated to the High Court's roll last year but has been denied a practising certificate by the society, meaning some types of work remain off-limits to him.
Earlier this month, he told the Otago Daily Times he "came up with the idea" for the website and helped design it, but was not working in restricted areas, was not involved in its continuing operation and did not profit from it.
Yesterday, society vice-president Anne Stevens, of Dunedin, said the society's scrutiny of the website had found that was correct.
However, the society believed anyone using the documents "should consult a lawyer at an early stage before finalising the terms of a separation agreement".
"What it means is he can do it but the parties can't rely on it."
That was because, under the Lawyers and Conveyancers Act, certain areas of work were reserved for lawyers, including certain legal advice and actions carried out in relation to property relationship agreements, she said.
The separate Property Relationships Act creates three key requirements which need to be met for a relationship agreement not to be void.
Each party to an agreement needed independent legal advice before signing, with each signature to be witnessed by a lawyer, and the lawyer witnessing the signature to certify that the party received an explanation by the lawyer as to the effect and implications of the agreement, she said.
"You get really close to stepping over the line because you can do hardly anything without being at the point where you need an actual lawyer to do it.
"As soon as you want a property agreement, you need independent legal advice and that has to be certified, otherwise the agreement won't stand up in court.
"It's not a reserved area of work as he advertises it, and you've got to take it on face value as it's advertised.
"It's not in breach at the moment."
However, Mr Guest said when contacted the provisions identified by the law society were spelled out on the website and in the documents when downloaded.
"The site advises for any difficult matter, or controversial matter, or disputed matter, they should see their lawyers."
Footnote: Last night the website was not offering a service to New Zealanders.
