The Commercial Court has begun hearing a challenge by a major developer to the National Asset Management Agency.
Paddy McKillen is challenging the transfer of €80m of loans from Bank of Ireland to NAMA.
The case is being heard by three judges presided over by High Court president, Mr Justice Nicholas Kearns.
NAMA's legal team is being led by the Attorney General, Senior Counsel Paul Gallagher - a measure of how seriously the case is being viewed by the State.
Opening the case, for Mr McKillen, Senior Counsel Michael Cush said Mr McKillen was not asking the court to decide if NAMA was a good or bad idea or a good or efficient model to deal with the state's difficulties.
He said he was not asking the court to rule on the merits of NAMA's decision to acquire Mr McKillen's loans or to rule on the merits of NAMA acquiring unimpaired loans. He said he was not asking the court either to rule on the valuations of assets or on whether Mr McKillen's loans constituted a systemic risk to the banking system.
He said Mr McKillen was basing his case on five issues.
He said the procedures adopted by NAMA in its interpretation of the act were a denial of Mr McKillen's constitutional right to fair procedures. He said NAMA failed to have regard to relevant considerations when exercising its discretion to acquire Mr McKillen's loans.
He said the decision to acquire the loans was taken before the establishment of NAMA and was therefore null and void and of no effect.
He said under a correct interpretation of the European Commission's decision approving NAMA, at least some of a borrower's loans must be impaired before they can be acquired by NAMA. Mr McKillen's final point is that if he is wrong on these issues, then the legislation itself is so broad that it is unconstitutional.
Mr Cush said Mr McKillen owned or had an interest in a property portfolio worth between €1.7 and €2.28 billion. He said he had loans with the banks participating in NAMA to a value of €2.1 billion.