[jveritas]

You cannot graduate from law school with a C. Minimum grade for graduation in graduate schools is a B. Probably most students in Law School graduate with A-

Why has not Obama release his undergraduate grades?

[Arguendo]

You can graduate from HLS (and most law schools) with a C average, though no one actually does. The average grade is about a B+.

No idea about his undergrad grades. They could show he got into HLS through affirmative action even if he eventually managed to succeed at law school anyway.