Interestingly one of the MPs who brought this to the European courts was David Davis, the cabinet minister who has the title 'Secretary of State for Exiting the European Union'
As long as he is part of the cabinet, we can assume Theresa May will at least be faced with internal opposition. And as long as the Tories have as slim a majority as they do, he will be one of the people guaranteeing that e.g. her ambition to abolish the Human Rights Act won't happen, as he's virtually certain to leave cabinet and stage a rebellion in the commons if she goes that far.
There's plenty of stuff he won't be able to stop, though, especially in cases where May can rely on Labour to prop her up.
I don't think his position makes it any more interesting though, this issue has little to do with the EU - other than it being the location of the appropriate court for as long as we remain in the Union.