New Zealand Herald editor-in-chief Tim Murphy said he expected artists using the newspaper's work to ask for permission and consult on what they intended to use the work for.
"The photographer who captures an image such as this is a professional who deserves recognition - that should not be converted by an artist without reference to us," Mr Murphy said.
However, Wanganui art dealer Bill Milbank, owner of the WHMilbank Gallery and former director of the Sarjeant Gallery, said Mr Rayer's artwork was "a valid thing to do".
"What he's done is a re-interpretation, and that is what art and artists do," Mr Milbank said.
"If every artist was sued for re-interpretation, artists by the score would be found to be in breach of copyright."
He said the career of New Zealand artist Dick Frizzell had been built around variations on the iconic Four Square grocery man. "That's a classic case of re-interpretation."
Mr Milbank said Mr Rayner's art had been known for "pushing the boundaries".
"That is what artists do - they don't shy away from controversy."
He said Black Widow was a high-quality piece of work.
"He isn't the first artist to respond to controversial figures such as Helen Milner.
"For the wider community, it's good that we don't forget their notoriety," Mr Milbank said.
In 2009 Mr Rayner and his brother Paul presented an exhibition of ceramic teapots with David Bain-head lids.
Mr Rayner could not been contacted because he is currently overseas.
