The board, which has been in tough negotiations with Portland Place staffers on the subject, refuses to provide assurances that non-architects closely involved with architecture who use the suffix 'Hon FRIBA' will not be prosecuted.
This leaves open the possibility of CABE's Paul Finch, Argent's Roger Madelin, Open House London's Victoria Thornton, former construction minister Nick Raynsford and TV presenter Kevin McCloud appearing in court for abuse of title.
And AJ editor Isabel Allen, who was made an honorary fellow earlier this year, may also have to consult her lawyers.
A recent document sent to the RIBA summed up the ARB's position.
It said: 'If you are in practice or carry on business in the United Kingdom relating to architecture or to the design and construction of buildings and you are not on the register then you are liable to prosecution if you use such style or suffix [as Hon FRIBA].'
Unsurprisingly the RIBA considers this position unhelpful. 'We consider that- [this] guidance perpetuates a very narrow interpretation of the 1997 Act and gives no comfort to many RIBA Honorary Fellows who are involved in fields connected to architecture, building design or construction,' the institute said in a statement.
'[The honorary members] are all very senior and respected figures in their respective fields, and it is nonsensical to suggest that they could be confused for registered architects.
'For example, we find it hard to conceive that the ARB refuses to give an assurance to Nick Raynsford MP that he will not be prosecuted under the Architects Act because he is the current Chairman of the Construction Industry Council.'