The applicants — Gerard Dowling, Padraig McManus, Piotr Skoczylas, and Malta-based firm Scotchstone Capital Fund Limited — had their case heard for the first time in the European Court of Justice yesterday.
While no date was set for the verdict, court officials confirmed a preliminary opinion by an EU judge is usually made within two to four months of the hearing.
A final verdict is likely by the end of the year.
IL&P was split into Irish Life and Permanent TSB.
The Government subsequently sold Irish Life to Canadian insurance giant Great-West Lifeco.
By 2010, the State had guaranteed deposits in IL&P amounting to €26bn. It then made legal commitments, under the EU-IMF bailout, to recapitalise all viable banks.
The banking and insurance group was nationalised in July 2011 after stress tests ordered under the bailout showed that the banking arm needed to raise billions of euro in new capital — which was later injected by the Government.
However, some shareholders said they could raise the capital privately, and voted against the order at an extraordinary general meeting at the time.
Those taking the case allege that Minister for Finance Michael Noonan breached EU company law by ordering the injection of funds.
The move had the effect of lowering IL&P’s share price, depriving them of earnings, they claim.
The case was referred to the EU court by the Irish High Court in February to check whether the recapitalisation — which was enforced under the Credit Institutions Stabilisation Act of 2010 - contravenes EU company law, which contains safeguards for the protection of shareholders in public limited liability companies.
A spokesman for the Department of Finance said the department would be “robustly” defending its case at the European Court of Justice.
“This matter is currently before the courts and is therefore sub judice,” the spokesman said. “We will therefore not be commenting other than to confirm that the litigation will be robustly defended.”