The suspension of three Ulster Unionist MPs from the party is invalid, the High Court in Belfast has ruled.
The three MPs' legal action was successful
Jeffrey Donaldson, the Reverend Martin Smyth and David Burnside were seeking an injunction to overturn the decision of a party disciplinary committee to suspend them.
They were suspended last month after resigning the party whip at Westminster in protest at the policies of UUP leader David Trimble.
The three MPs were seeking a ruling that the party officers' action was illegal.
Mr Justice Paul Girvan said on Monday that the suspension was invalid because the disciplinary committee set up by the Ulster Unionist Party officers had been "improperly constituted".
The ruling means that the MPs are once again members of the Ulster Unionist Party.
The court ruled that the participation of one member of the
committee, Barry Fitzsimons, could be questioned because he was involved in a
motion of no confidence against Mr Donaldson in his Lagan Valley constituency.
However, the court ruled that the participation of Mr Trimble in a meeting considering what action should be taken against the three MPs was proper.
Costs were awarded against the Ulster Unionist Party.
A disciplinary hearing has been scheduled to take place on 17 July.
After the court ruling, Mr Donaldson said: "Justice has
Mr Donaldson, who was joined in the court by Mr Smyth, appealed to Mr Trimble to
abandon the disciplinary action.
He said: "I would say to Mr Trimble: draw back from the
"If you want a way forward, this is not it. Suspension is not the way forward.
"It is time for Mr Trimble to start listening to what we have to say instead
of resorting to a rulebook that he cannot even interpret, and which this court
has determined to have been an unlawful decision."
Former Ulster Unionist assembly member Peter Weir, who is now a member of Ian Paisley's Democratic Unionists, was among those in the public gallery.
Former Stormont environment
minister Dermot Nesbitt and the UUP's chairman James Cooper were also present.
Chairman of the Ulster Unionist Party James Cooper said the party
leadership would now engage in a "mature reflection" on the judgment.
However, he said the judge had "clearly upheld" the decision of the party officers to make a reference to the disciplinary tribunal.
"What he found at question was the terms of reference," he added.
Mr Cooper said it was "highly regrettable" that Ulster Unionists were
fighting each other in the courts.
But he added: "We do not want to
have to use disciplinary procedures, but we cannot continue to have an assault
going on from within."
The three MPs quit the whip in a move designed to increase pressure on Mr Trimble by refusing to endorse his policy on the British-Irish joint declaration.
Last month, dissident unionists gathered 30 signatures for a motion of no confidence in David Trimble as Member of Parliament for Upper Bann. It is due to be discussed on Tuesday.
A similar party vote in the Lagan Valley constituency against Mr Donaldson was dropped "in the interests of party unity" following his narrow defeat in a vote taken by the UUP's 900-strong ruling council.
In June, Mr Trimble narrowly fended off a challenge from party rebels, led by Mr Donaldson, who wanted the party to reject the recent British and Irish joint declaration.
The joint declaration, released in May, outlined plans to reduce troop numbers to 5,000 as part of an attempt to move the Northern Ireland political process forward.
It included five annexes dealing with security normalisation, policing and justice, human rights and equality, on-the-run paramilitaries and mechanisms to verify and monitor any deal.
Northern Ireland's devolved administration was suspended last October amid allegations of IRA intelligence gathering in the Stormont government.