The EIS is seeking an interdict to stop Edinburgh holding a disciplinary hearing under procedures that have not been agreed with the union.
A full hearing at the Court of Session would be the first legal challenge to disciplinary arrangements imposed in the face of union opposition. These transfer the power to sack teachers from education committees to the directorate. There is then a right of appeal to a subcommittee of councillors which, in Edinburgh, is an offshoot of the education committee.
An assistant head in an Edinburgh secondary school, who has been suspended on full pay since last June, was due to appear before a senior education official on Monday to answer charges of misconduct. The hearing was postponed when the EIS declared its intention to serve the interdict.
Edinburgh says a new disciplinary code was approved last April and must be adhered to.