A Chartered Accountant is fellow of ICIA which is a legal body and as such role of CA is defined under various legislations. for example Tax Audit Report and various other certificates can only be signed by a CA only.
A tax consultant may or may not posess formal Law degree. Income Tax Act recognises even its own retired officers as Regd Tax Practioner by virtue of passing a prescribed departmental exam.
Yes, a consultant, if he posess LLB or above degree can appear before the courts which a CA can't do. But then who stops a CA from obtaining a law degree?