The judicial review proceedings will argue that the new checks on goods moving from Great Britain to Northern Ireland were imposed without the consent of the public.
Ms Foster is joined by DUP deputy leader Nigel Dodds, the party’s Westminster leader Sir Jeffrey Donaldson and chief whip Sammy Wilson, as well as former Brexit Party MEP Ben Habib, Eurosceptic peer Kate Hoey and Jim Allister, the leader of the Traditional Unionist Voice party.
She said: “Fundamental to the Act of Union is unfettered trade throughout the UK.
“At the core of the Belfast Agreement was the principle of consent yet the Northern Ireland protocol has driven a coach and horses through both the Act of Union and the Belfast Agreement.
“Neither the Northern Ireland assembly, the Northern Ireland executive nor the people of Northern Ireland consented to the protocol being put in place or the flow of goods from GB to NI…