Developer Paddy McKillen has won part of his challenge to the National Asset Management Agency.
The Supreme Court ruled that the decision made to acquire Mr McKillen's €2.1bn portfolio of loans had no legal effect.
It ruled that the decision was taken by an interim team on 11 December and 14 December in 2009, before the establishment of NAMA on 21 December of that year.
The court found that NAMA could have made a valid decision after it had been established.
But the consistent assumption by NAMA was that the decision had been made by the interim team and it did not see any necessity for a further decision.
The court found that contrary to the High Court's judgment, the interim team's decision was not given legal effect by any subsequent act or series of acts by NAMA.
It said the question of whether NAMA had made a decision to acquire Mr McKillen's assets was not a purely technical and formal one. It said such a decision was an essential step in the statutory process.
The court found that it was of critical importance in this case that NAMA had never reached the stage of serving the financial institutions involved with an acquisition schedule for Mr McKillen's loans.
The court found against Mr McKillen on the issue of the European Commission's approval of NAMA. It found NAMA had not breached the commission's decision to approve the agency.
The court will sit next Wednesday to hear submissions on what will happen to the other issues in Mr McKillen's appeal - the right to fair procedures, the failure of NAMA to take into account relevant factors and the constitutionality of the legislation - in the light of the fact that the court has ruled there is no decision by NAMA.
The Supreme Court's ruling today could simply mean that the NAMA board can now make an official, valid decision to acquire Mr McKillen's loans and start again with the process of acquiring them.