The Parades Commission has been told to reconsider its decision not to restrict an Orange Order parade at Drumcree.
Parades at Drumcree have been peaceful for the past three years
The High Court ruling came after Garvaghy Road Residents challenged the commission's decision.
Saturday's march was arranged to mark 3,000 days since Orangemen were barred from marching along the mainly nationalist Garvaghy Road in Portadown.
A judge said the commission was told there was no general call-out but the lodge's website contradicted that.
Mr Justice Weatherup said Portadown District Lodge on its website had called for Orange Order members throughout Northern Ireland to join the march at Drumcree Hill.
But he said the Parades Commission had been told there was no general appeal for support when it made its decision.
"It seems to me that the Parades Commission proceeded on the basis of the assurance there was no general call-out but that is incorrect in view of the website," said the judge.
"The commission has been given an ill-founded assurance and accordingly that is a relevant consideration which requires to be taken into account in relation to their decision to issue no determination."
The commission will discuss the matter on Saturday.
A commission spokesperson said: "We welcome the fact that the commission's decision-making process has been upheld and validated.
"The court has raised an issue on the numbers of participants and asked the commission to clarify the numbers."
Breandan MacCionnaith, spokesman for the Garvaghy Road Residents Coalition, said the court had "vindicated the criticisms we made".
"Hopefully, now that the commission has been ordered by the court to look again at the issue we will now see common sense restrictions being put on the parade with the result that tensions will be defused over the weekend," he said.
Each July, the Portadown Orange Lodge attends a service at Drumcree church to commemorate the anniversary of the Battle of the Somme.
Since 1998, their homeward route has been blocked by the security forces, following a determination by the Parades Commission.
The parade has been marked by serious violence in the past, but it has passed off peacefully in the last three years.
The march has been one of Northern Ireland's most contentious. The route was last used by Orangemen in 1997.
The Parades Commission was set up in 1997 to make decisions on whether controversial parades should be restricted.
The Orange Institution is the largest loyal order in Northern Ireland.
Its origins date from the 17th century battle for supremacy between Protestantism and Catholicism. Prince William of Orange, originally of the Netherlands, led the fight against Catholic King James.