i've been allocated a supervisor with expertise in immigration law, when my proposed topic is european public law. should i be concerned / ask the university for an alternative supervisor? i had assumed that law phd supervisors' research areas should match student proposals! please advise if possible : )

It's always a good idea to have a supervisor who's interest and expertise lie in the same areas as your own. If you are funding this PhD yourself then you should probably complain. If the funding is tied to the supervisor or has been allocated by the department then there may be little that you can do. If they are reluctant to allocate a new lead supervisor then you should try requesting a second supervisor who has experience in your research area.

Thanks for your help. The funding is tied to the university. I believe the possible supervisor volunteered, but really seems to be pressuring me to sway my research to his favoured area - which I don't want to do! Hope I can resolve this without antagonising people.