Supreme Court President David Neuberger questioned Pannick on Wednesday over whether parliament needed further involvement.
He is representing Gina Miller, the investment fund manager and philanthropist who won a historic High Court ruling on November 3 that Prime Minister Theresa May lacked prerogative powers to notify Article 50 without consulting MPs.
The lawyer acting against the government, Lord Pannick, said the "political significance" of June's vote was "irrelevant" to the legal battle.
Triggering Brexit will "frustrate or render insensible" a large number of United Kingdom laws and is a reason why Parliament must be involved, a top lawyer has told the Supreme Court.
Mr Eadie said such an act "certainly won't" disclose details of the Government's negotiating strategy - a position which later seemed to be negated by Downing Street after it said it would publish its Brexit plan before triggering Article 50 in order to stave off a likely defeat in the House of Commons this week.
Mrs May has made it clear she still intends to give an Article 50 notification by the end of next March to start the leave negotiations with 27 other European Union countries.
The government will argue the Prime Minister has the right to unmake treaties under so-called prerogative powers and will focus its arguments on the fact that Britain has a dualist constitutional system, meaning government decisions on the global plane can sometimes impact domestic law.
The case has generated huge interest both in Britain and overseas and has been seized upon by both Remain and Leave campaigners, with the Daily Mail labelling the three High Court judges who gave the ruling "Enemies of the People" to widespread public condemnation.
The powers enable decisions about joining or leaving worldwide treaties to be made without a parliamentary vote.
Mr Eadie said upholding the High Court ruling would have the effect of introducing a "newly-discovered principle" into British foreign policy by which Parliament would have to pass "primary legislation" for each new worldwide treaty or similar overseas development to have effect.
He said on Tuesday, the second day of a four-day hearing, that it would be "quite extraordinary" if the 1972 Act "could be set at nought by the actions of a minister acting without Parliamentary authority".
Britons voted for Brexit by 52 to 48 per cent and the government has said this mandated it to begin the divorce process using the prerogative power.
He said if judges ruled against the government, "the courts would be imposing in effect a new control of a most serious kind" on the government's ability to make worldwide treaties. The case is due to finish on Thursday with a ruling in the new year.
Later on Wednesday, the Scottish government's top law officer will argue that Holyrood should also have a say before Article 50 is triggered.
"At the heart it really is as straightforward as that".