Confidential legal advice obtained by the ASTI says the current attempt to remove its general secretary, Mr Charlie Lennon, could breach his contract and expose the union to a very expensive legal challenge.
In a letter to the union's president, Mr P.J. Sheehy, ASTI's legal advisers say that the move against Mr Lennon "could have very serious consequences for the ASTI, not least the costs associated with trying to defend an indefensible legal position".
The legal advice appears to remove any immediate threat to Mr Lennon's position.
On Friday, a meeting of the union's central executive council was mandated to hold a further meeting; this is due to consider the establishment of a special seven-member committee to review Mr Lennon's performance. A date for the meeting has still to be scheduled.
ASTI sources say Mr Sheehy has no intention of calling the meeting until all the legal issues are resolved. He appears determined that the union will not be exposed to a very expensive legal action by Mr Lennon. Sources say Mr Sheehy also wants to uphold the rules of the association, its contractual obligation to Mr Lennon and the rules of natural justice.
In their letter, the ASTI legal advisers, BCM Hanby Wallace, state that Irish law contains significant guarantees to ensure due process and fair procedure and that these rights have been "vigorously upheld" in the courts.
The letter, written by Mr Gary Byrne, a partner in the law firm, reminds the union of an agreed complaints procedure governing Mr Lennon and all other head office staff. "Failure to follow that agreement would amount to breach of contract of the part of the ASTI," he warns.
The legal advisers also warn that if the current review process continues, Mr Lennon is likely to be successful in obtaining an injunction, which would prevent it from continuing.
A performance review of the type suggested by some in the union "could be deemed to be prejudicial to the general secretary's interests and rights". By insisting on a further CEC meeting members could create a situation where those concerns "could never be addressed", the letter warns.
A section within the union is pressing Mr Sheehy to convene the CEC meeting within the next fortnight and clear the way for a review of Mr Lennon's performance.
The Lennon camp maintain he is being opposed by a hardline faction who refused to heed his advice during the pay campaign.
Some ASTI members predicted last night that it would be left to the next union president, Mr Pat Cahill, to decide on whether to establish the review committee.
Mr Cahill, who succeeds Mr Sheehy in August, has been a vocal critic of the ASTI leadership during the campaign.
By contrast, Mr Sheehy spoke warmly of his working relationship with Mr Lennon in an Irish Times interview last week.