Outspoken host Nick Ferrari tore into John Shaw, from the Fair Deal For Expats, which had their case attached to Gina Miller's Article 50 Brexit challenge, as he asked what gave them the right to delay the UK's democratic decision to abandon Brussels.
Mr Shaw, speaking outside the Supreme Court on Tuesday, said he was delighted at the ruling and said the decision had meant "life or death" for millions across Europe.
Speaking to Mr Shaw before the verdict was announced, LBC host Ferrari asked: "You've decided to live away from this country, yet you are seeking to, at best, delay the will of people who have chosen to stay here.
"What gives you the right to do that?"
To which Mr Shaw responded: "We don't believe that is necessarily the case."
GETTY • LBC
Nick Ferrari demanded what gave Fair Deal for Expats the right to thwart Brexit
Less than impressed, Ferrari demanded: "Well yes of course there could be a time delay. Let's be candid with each other it is not going to help matters is it?
"You've chosen not to live here though, that is what some of my listeners would say, you don't even live here, why are you holding up the will of the people who live here?"
Having none of it, the Mr Shaw insisted they had a right to be heard as he told LBC: "We are British to our core. All our friends are British.
"We don't want to give up our British citizenship and we have the right, like everyone else, to live and reside in any part of the world."
Mrs May must secure the consent of Parliament before triggering Article 50
You are seeking to, at best, delay the will of people who have chosen to stay here
The clash of opinion came just hours before the Supreme Court ruled on Tuesday that Theresa May cannot trigger Article 50 without an Act of Parliament.
In a verdict upholding the High Court's decision that the official process of leaving the European Union cannot start without a Parliamentary vote, the UK's most senior court dismissed the Government’s appeal against last November’s verdict.
Lord Neuberger, President of the Supreme Court, said: "The referendum is of great political significance, but the Act of Parliament which established it did not say what should happen as a result.
"So any change in the law to give effect to the referendum must be made in the only way permitted by the UK constitution, namely by an Act of Parliament.
BREXIT: Supreme Court Ruling
Tue, January 24, 2017
Britain's most senior judges ruled that Prime Minister Theresa May does not have the power to trigger the formal process Article 50 for the UK's exit from the European Union without Parliament having a say.
1 of 12
Issued by the Supreme Court of (top row, from the left) Lord Neuberger, Lord Mance, Lord Kerr, Lord Sumption, (bottom row, from the left) Lady Hale, Lord Clarke, Lord Wilson and Lord Hodge, who agreed with the majority decision that the Government could not trigger Article 50 without Parliamentary approval.
"To proceed otherwise would be a breach of settled constitutional principles stretching back many centuries."
Attorney General Jeremy Wright, who presented the Government's case during the Supreme Court hearing, said: "Of course the Government is disappointed with the outcome.
"The Government will comply with the judgement and do all that is necessary to implement it."
The decision means Mrs May has 67 days to secure the consent of Parliament before triggering Article 50 if she wants to adhere to her own deadline.