The chief constable will be allowed to challenge a coroner's direction to hand over edited copies of secret reports into 1980s "shoot-to-kill" incidents.
A High Court judge said Matt Baggott could seek a judicial review of senior coroner John Leckey's decision.
Six people, including IRA members, died in the controversial shootings by the Royal Ulster Constabulary.
The results of an investigation into whether the police set out to kill them have never been made public.
In 2007, at a preliminary inquest into the deaths of IRA men Sean Burns, Eugene Toman and Gervaise McKerr near Lurgan, County Armagh in 1982, the coroner said he could see no reason why the reports could not be released to him.
He repeated his request last September and set a November 2009 deadline for the handing over of reports by former Greater Manchester Police Deputy Chief Constable John Stalker and Sir Colin Sampson of the West Yorkshire Police.
With police emphasising the volume of material and complex issues involved, deadlines set for handing over the material have not been met.
The confidential reports are said to contain significant information that was not available when an original inquest into the deaths was held in 1983.
The coroner's inquiry has also widened to include the deaths of three RUC officers - John Quinn, Allan McCloy and Paul Hamilton - who were killed by an IRA landmine the same year.
Lawyers for the chief constable argued on Monday that a sequence should be adopted where the coroner reads the material and indicates which parts he considers relevant.
State agencies would then decide whether a Public Interest Immunity application was needed.
If any certificate was granted redactions could be made and then the documents handed over, according to police lawyers.
But the coroner's legal representatives said there was nothing unlawful about the current arrangements.
Lawyers for the victims' relatives told the High Court their human rights were being violated by the delay in holding inquests.
Granting leave to seek a judicial review, Mr Justice Gillen ruled that the police had established an arguable case on points claiming the coroner erred in law and acted in breach of the chief constable's procedural legitimate expectation.
The case will now proceed to a full judicial review hearing in May.