While the group's plans have not been explicitly outlined yet, it seems likely this action will take the form of a judicial review.
The latest row between the reformers and the board's leadership centres on a small retention fee rise of £1.50.
The reform group - which won the lion's share of the vote in the last ballot standing on a ticket of paring back the ARB's work - believed they had defeated the rise two weeks ago by threatening to walk out and leave the board inquorate.
But just days later the vote was put to board members again, but this time by post. Reform group members argued that this move, which resulted in a nine-to-one result in favour of the rise, contradicted the Architects Act, and boycotted it.
However, new ARB registrar Alison Carr declared the vote acceptable last Friday and the retention rise therefore became board policy.
But now the reform group is threatening legal action. 'What we are saying is that because we are not voting the ballot of board members was inquorate,' reform group member George Oldham said.
'We will test the decision in law of [the board leadership's] attempt to enforce the rise,' he warned.