Lawyers for Lord Trimble have told him that his Brexit legal challenge cannot be heard in court at this stage.
He is attempting to challenge the legality of the backstop, arguing it breaches the Good Friday Agreement.
An update on a crowdfunding site being used to raise money for the action says "there is broad agreement from counsel that the case cannot be heard in a court of law at this stage."
It adds "we have asked for opinions as to when that situation might change".
That legal advice came after government lawyers replied to Lord Trimble's initial claim.
They argued that the case was not capable of being argued in court because no final decision has yet been taken on the backstop and therefore there is nothing for a court to review.
The update said that the government lawyers made no response to the "substantive legal basis" of the potential judicial review.
It adds that a set of additional legal opinions has now been commissioned to "test and develop the grounds for our claim as part of our case preparation."
Lord Trimble and his supporters say these legal opinions can also be used to "inform and equip the UK government" as it tries to get changes to the backstop.
It concludes by stating: "We are alert to the potential for a judicial review in the future if the final agreement reached between the UK and the EU fails to uphold the Belfast Agreement."
The crowdfunder has so far raised £28,000 of a £50,000 target.