The Civil Public and Services Union is to seek full payment of wages to its members who were taken of the payroll by the Department of Agriculture in April 2003.
The decision comes after a Supreme Court ruling to uphold a High Court judgment that the Department had acted above its power in dismissing the workers for their part in 'limited industrial action'.
The action involved the workers refusing to carry out some of their duties as the pursued the addition of promotional posts promised after the Foot and Mouth Crisis.
It lasted 13 weeks and involved workers from offices in Casltebar, Galway, Limerick, Tralee and Clonakilty.
The CPSU estimates that the repayments will total €1.5m.
The Department had argued that the decision to remove the workers from the payroll was covered under Section 16 of the Civil Service Regulation Act 1956.
However the Supreme Court ruled that "the partial withdrawal from work duties does not constitute unauthorised absence from duty under Section 16", and awarded legal costs against the Departments' of Agriculture & Finance.
CPSU Financial Secretary, Eoin Ronayne, welcomed the decision saying, "fair play demands that where an employer has been found not to have had the power to take someone off the payroll but did, as in this case, then the workers involved have every right to have their wages paid for the period of the unlawful deductions."