A decision to approve Northern Ireland's biggest roads project is to be quashed, a High Court judge confirmed on Friday.
Mr Justice McCloskey made the order after the Stormont department who gave the go-ahead for the A5 Western Transport Corridor scheme announced it was no longer defending a legal challenge.
The outcome is based on the decision having been given in the absence of a minister.
The multi-million pound roads project linking counties Derry and Tyrone now faces further uncertainty and potential delay.
It would involve a new 85km trunk road running from New Buildings, via Strabane, Newtownstewart, Omagh and Ballygawley, and terminating near the border at Aughnacloy.
Construction on phase one was due to begin early this year at a cost of £150m.
But that was put on hold after fresh judicial review proceedings were launched by umbrella group the Alternative A5 Alliance.
In 2013 the group, made up of landowners, farmers and supporters, won its first legal action against the project.
At that stage a judge quashed the decision to press ahead with the scheme, which forms part of a proposed key cross-border business route linking Dublin and the north west, due to a breach of a habitats directive.
In November last year the Department announced its decision to proceed with the planned route - prompting the renewed challenge.
Lawyers for the Alliance were set to contest the legality of the decision being taken by the Department's Permanent Secretary in the absence of a Minister.
Their position was strengthened by a landmark ruling earlier this year in a case over a planned incinerator near Belfast.
The Court of Appeal held that a senior civil servant did not have the legal power to take such decisions without a Minister being in post.
Even though new legislation has been brought in to give greater clarity, issues still surround existing challenges.
On Thursday counsel for the Department said it was no longer considered in the public interest to defend the Alternative A5 Alliance's case.
He asked the court to quash the relevant decision, referring to it being taken in the absence of a minister.
With the Alliance given time to consider the proposal, their solicitor, Roger Watts, confirmed today his clients did not object to the outcome.
Mr Justice McCloskey then made the quashing order sought.