Instances of this class are thrown by BCEL's class file verifier "JustIce" when a class file to verify does not pass the verification pass 3 because of a violation of a structural constraint as described in the Java Virtual Machine Specification, 2nd edition, 4.8.2, pages 137-139. Note that the notion of a "structural" constraint is somewhat misleading. Structural constraints are constraints on relationships between Java virtual machine instructions. These are the constraints where data-flow analysis is needed to verify if they hold. The data flow analysis of pass 3 is called pass 3b in JustIce.