The two-day High Court hearing is set to finish on Tuesday
The judges hearing millionaire Stuart Wheeler's attempt to force a referendum on the EU Treaty have reserved their judgement after a two day hearing.
Mr Wheeler said a vote was promised and "fair play" meant it should be held.
Prime Minister Gordon Brown says the treaty does not have the constitutional implications to merit a referendum.
Lord Justice Richards confirmed that, as expected, judgement was being reserved - but promised a decision "as soon as possible".
On the second day of the case Clive Lewis QC, for the Commons Speaker Michael Martin, said that parliamentary privilege prevented a court from ordering MPs or ministers to introduce bills.
He said there was a natural division between the realms of law and politics and that Mr Wheeler's complaint fell within the realm of politics.
On Monday, Rabindher Singh QC, counsel for Mr Wheeler, told the High Court the Tory donor had a "legitimate expectation" there would be a public vote.
"The government promised a referendum and should keep its promise," he said.
At stake were the fundamental principles of "good administration, fair play and straight dealing with the public".
Mr Singh said ex-prime minister Tony Blair had promised a referendum prior to the ratification of the Constitutional Treaty, which came to nothing after plans for an EU Constitution were rejected by French and Dutch voters in 2005.
That promise had given rise to "a procedural legitimate expectation that a referendum would be held in respect of that treaty - and by implication any treaty containing substantially similar terms, whatever its name".
Lord Justice Richards and Mr Justice Mackay were told the evidence showed that the subsequent Lisbon Treaty and the Constitutional Treaty were all but the same, except in name - a charge rejected by the office of the prime minister's counsel.
But Mr Brown had unlawfully failed to honour the government's promise of a referendum, Mr Singh said.
However, Lord Justice Richards asked "about the extent to which the courts can become involved in policing the political process".
Mr Singh argued that the courts "in the last 25 years have never shrunk from addressing and answering the crucial question as to whether there was an error of law disclosed to the court".
But Jonathan Sumption QC, appearing for the office of the prime minister, asked the court to reject Mr Wheeler's case claiming it was "politics dressed up as law".
If Mr Singh's argument was accepted, judges could become involved in a range of political issues where assurances had been given to the electorate at large "including those to reduce the burden of taxation, improve educational standards, half class sizes, double the size of the Navy or whatever you would like", he said.
The two-day review was heard as voters in Ireland, the only EU state holding a referendum, prepare to go to the polls on Thursday.
The treaty, which paves the way for greater European integration, an EU presidency and the abolition of a host of national vetoes, will effectively be killed off if Ireland votes "no" as it must be passed unanimously by all 27 states.
In March, MPs in the House of Commons voted by 346 votes to 206 to approve the EU (Amendment) Bill.
The Bill - now in the Lords - will ratify the Lisbon Treaty, which was drawn up to replace the EU constitution after that was rejected by French and Dutch voters in 2005.
Row over Lib Dems
Shadow foreign secretary William Hague has written to Lib Dem leader Nick Clegg asking him to clarify his party's position on the Lisbon Treaty.
It comes after Lib Dem MPs were ordered to abstain on the vote on a referendum in the Commons, yet the leader of his party in the Lords has indicated that peers there will be whipped to oppose it.
In his letter, Mr Hague asked Mr Clegg if he had "lost control" over his party.
"Or is it because your real objective is to see the Lisbon Treaty in force at all costs before the British people have a chance to have their say?"
The House of Lords is due to vote on calls for a referendum on Wednesday.