A pan-unionist legal challenge to the Northern Ireland Protocol will be heard next month, a High Court judge confirmed on Tuesday.
Mr Justice Colton set aside up to four days for the bid to judicially review the UK government over the post-Brexit trading arrangements.
Proceedings brought by Traditional Unionist Voice leader Jim Allister are being backed by senior Democratic Unionist Party and Ulster Unionist Party representatives.
In court on Tuesday senior counsel for Mr Allister stressed the need to have all preliminary legal issues in advance of the main hearing.
John Larkin QC, the former attorney general for Northern Ireland, said: "In a case of this importance it's imperative that no party is rushed into an inadequate or half-cocked approach."
The cases involve claims that the protocol breaches the Act of Union.
Amid disruption to business at Irish Sea ports, unionists are contesting the lawfulness of the new arrangements.
The protocol, which formed part of the Brexit deal between the EU and UK, was aimed at preventing a hardening of the land border on the island of Ireland.
Under the terms of the protocol Northern Ireland remains in the EU single market for goods.
But it has also led to checks carried out on goods coming into the region from the rest of the UK.
A previous court was told an assertion by Secretary of State Brandon Lewis that there is no Irish Sea border does not match the legal reality.
Although three separate challenges were originally being planned, one case brought by UUP chairman Lord Empey has been withdrawn.
Loyalist pastor Clifford Peeples has also issued proceedings against prime minister Boris Johnson, contending that the protocol breaches the Belfast (Good Friday) Agreement.
The Belfast man’s lawyers maintain that such a constitutional change cannot take place without a referendum.
However, Mr Justice Colton insisted Mr Peeples’s action will only be allowed to progress if it involves separate legal points.
“Why should the taxpayer pay for a case when there’s an ongoing case which raises, as far as I can see, virtually the same issues?” he said.
Listing a further review later this month, the judge asked Mr Peeples’s legal team to set out their distinctive grounds of challenge.