Doubt they will ask you anything that is too specific unless you’ve done Law at A Level as they wont expect you to have any knowledge yet.
Just make sure you know the course layout, the prospectus, and know your own ucas application as you dont want to trip over your own feet. Furthermore, read the papers and keep upto date on matter as that will be the issues they are more likely to ask about, and more likely to see how you form your opinion on an issue.
Also try and think of some questions to ask them, then it should feel less or an inquiry!