This paper examines the struggle between the legislative and judicial branches by focusing specifically on congressional influences on the behavior of federal judges. We argue that Congress may constrain individual judicial behavior by passing statutes containing detailed language. To test this thesis we borrow from the bureaucratic politics literature to introduce and test a new measure of statutory constraint. Using data from the U.S. Courts of Appeals we find that appellate court behavior is constrained significantly by statutory language, although this constraint is asymmetric across ideology. We discover substantial differences between Democratic and Republican appointees both in terms of statutory constraint and ideological voting. The data indicate judges appointed by Democratic presidents are constrained by statutory language in criminal cases. Similarly, Republican appointees are constrained by statutes in civil rights cases. Yet, neither Democrats nor Republicans are constrained in economic cases.