Which has precedence? Case law or newly enacted law on same subject

I assume that by "newly enacted law" you mean a statute.  If so, that takes precedence.  "Case law" interprets statutes (I'm just using statutes as a generic terms to include all laws enacted by legislative or administrative bodies.)  If that changes validly (meaning that if the new statute doesn't violate a higher statute, for example a statute which violates the U.S. Constitution), and affects the basis of a prior "case law" ruling, the prior ruling is no longer controlling precedent.