No court can prevent the British government implementing the will of the people, a lawyer has told the second day of a legal bid in Belfast to try to stop the UK's planned departure from the European Union.
UK Prime Minister Theresa May plans to trigger negotiations with the European Union next year following June's referendum vote.
The ministerial power is the "common currency" of withdrawal from international treaties like the one governing Britain's membership of the EU, a barrister for the state said.
A cross-community group of politicians and victims campaigners at the High Court in Belfast is challenging the prime minister's right to launch the process.
Government lawyer Tony McGleenan QC said: "There is no legal impediment to government giving effect to the will of the people."
He noted the UK joined the EU through prerogative (ministerial) power. "It can withdraw using the same power."
The UK government plans to repeal the 1972 European Communities Act (ECA). The Act gives direct effect to all EU law and the introduction of a new Bill to repeal it will mean the Act ceases to apply from the day of exit.
The UK is party to the 2009 Lisbon Treaty which agrees relations with its European neighbours.
Mr McGleenan said ministerial prerogative was regularly used for withdrawing from international treaties.
The barrister added: "It is not illegitimate, unorthodox or undemocratic to use a prerogative power in that context."
Mr McGleenan said there will be a process of negotiation then parliament would be involved in modifying domestic laws.
"The prerogative power is an appropriate power to use in this context. There is nothing unorthodox about the course government proposes to take."
Some 56% of voters in Northern Ireland voters backed Remain in the 23 June referendum but some unionist-dominated areas supported Leave. The largest political party in Northern Ireland, the Democratic Unionists, campaigned for an exit.
Yesterday lawyers opposed to Brexit argued Northern Ireland has a veto over withdrawal from the EU.
