Ulster Unionist peer Lord Rogan played the role of Lord Speaker in Westminster as Boris Johnson's Brexit Bill took the penultimate step before being made law.
On Wednesday, MPs rejected all five amendments made to the bill in the House of Lords earlier this week - including modifications on citizens' rights, judiciary independence, the power of UK courts to diverge from UK law and the consent of the UK's devolved administrations.
They also removed an amendment which would have asked the UK government to negotiate an agreement with the EU to allow unaccompanied minors who have claimed asylum in another country and have a relative in the UK to be re-united with them.
It was returned to the Lords where peers backed down rather than challenge the authority of the elected chamber.
Deputy Speaker Nigel Evans later announced the European Union (Withdrawal Agreement) Bill has been granted royal assent and officially signed into law ahead of the January 31 deadline.
Lord Rogan (77) was on the Woolsack on Wednesday, where the Lord Speaker in the House of Lords sits, as the Withdrawal Agreement cleared its final parliamentary hurdle.
He said it felt like a significant landmark in the history of the United Kingdom.
The peer, who was born in Dromore, has served as Deputy Lord Speaker since March 2018 and stood in place of current House of Lords Speaker Lord Fowler.
Lord Rogan said: "As I made clear in two speeches in the House of Lords earlier this month, I believe that Boris Johnson and his Conservative Government have betrayed the people of Northern Ireland by agreeing to place a virtual border in the Irish Sea after Brexit.
He said he hopes the Prime Minister will drive a harder bargain with Brussels in upcoming trade agreement negotiations to ensure what he described as an "outrageous" barrier with Britain is removed.
"In the meantime, it is important that Northern Ireland peers and MPs continue to speak up for the Province in Westminster and make the feelings of our people and businesses known loud and clear."