They want clarification as to whether a century-old ruling on the employment of trustees - which says they may not benefit from the charity for which they are responsible - should apply in this case.
The National Confederation of Parent-Teacher Associations is seeking counsel's opinion in the face of a highly critical report into the 40-year-old organisation by the Charity Commission.
Judith Wood, chair, said she would dismiss the trio if legal advice backed the Charity Commission ruling. In the meantime the organisation was standing by the three officials.
Margaret Morrissey, press officer, Andrew Smetham, treasurer, and Belinda Yaxley, membership secretary - all former trustees - "may have benefited from their position of trust", according to the Charity Commission report.
It suggested that they resign and possibly pay back thousands of pounds in salary. None is expected to do so, and last week Mrs Morrissey, who was given an OBE for her work, wrote to the Queen asking for help.
She has also written on behalf of herself and the other employees to Richard Fries, chief commissioner at the Charity Commission, saying they did not believe they had breached charity law. "We feel our civil liberties are being abused," Mrs Morrissey wrote. "We are used to supporting parents who are being given a rough deal ... but we are now helpless and in your hands."
And she told The TES: "It cannot be natural justice that a person who answers an advert and is interviewed for a job can be told seven years later that technically the people who did that made a mistake and you should resign. "
Last week The TES revealed that the NCPTA was warned two years ago by Sandi Marshall, a former trustee, that key officials could be in breach of the law.
She instigated the commission investigation with Sean Rogers, the former chair elect. Both were removed by the NCPTA's executive last November.
The commission has granted an interim order which sanctions the continued employment of the three officials but has pledged to "monitor the issue".
Its investigation into alleged improprieties in the NCPTA, which represents parents of children in 11,500 state schools, accused the charity of running up large hotel bills and high expenses.
The NCPTA contests much of the 36-page report and trustees are now combing through it and seeking evidence from the office files to disprove it. Mrs Wood said that once she had formulated a response she would seek a meeting with the Commission.
"Some people want the report retracted. I don't. I am happy with the recommendations but I believe the Commission failed in its duty to be fair. "
Among the 34 recommendations is the call for a complete strategic review of the charity. Trustees are also urged to take legal action to regularise the position relating to the employment of former trustees.
Ms Marshall and Mr Rogers said they felt vindicated by the report's finding. They are now seeking an apology and damages, and want to be reinstated as trustees. Their solicitor this week wrote to the Charity Commission protesting about the lack of action on its recommendations. The letter asks the Commission to reconsider whether the trustees should be immediately removed from office.