Lagan Valley MLA and former Stormont Health Minister Edwin Poots.
Challenging a ruling that the prohibition was irrational, counsel for Lagan Valley MLA Mr Poots and his ministerial successors argued that devolved powers gave them the right to take a different position on the prohibition.
Attempts are being made to overturn a finding that the DUP MLA did not have power to keep the lifetime ban on donations from homosexual men.
A High Court judge held that his decision was irrational and “infected” with apparent bias.
The bar on gay men giving blood, put in place during the 1980s Aids threat, was lifted in England, Scotland and Wales in November 2011.
It was replaced by new rules which allow blood from men whose last sexual contact with another man was more than a year ago.
But Mr Poots maintained the ban in Northern Ireland on the basis of ensuring public safety.
Lord Chief Justice Sir Declan Morgan, sitting with Lord Justices Gillen and Weir, is examining issues about whether authority for blood policy is a devolved matter.
The hearing at the Court of Appeal in Belfast had been put on hold pending the outcome of a European Court of Justice case.
In April it ruled that a lifetime ban may be justified in member states, but only if there are no effective detection techniques.
The court heard that following the judgment from Europe an assessment on whether the ban is proportionate will now have to be carried out.
The appeal continues.