The core of Classpath Helper is a classloader that does more than just loading classes into the JVM. Classpath Helper not only records the exact location where a class is loaded, it also searches the classpath in proper order (including hierarchies of classloaders) looking for other locations for that same class. It verifies the bytes to determine if the class bytes from blocked classes are the same or different.
Classpath Helper also reads the byte code directly searching its class definition for dependencies on other classes. A reference to a class not found on the classpath would normally cause a ClassLoader to fail with the well known ClassNotFoundException or NoClassDefFoundError, but Classpath helper is able to bypass these limitations with its independent reading of the byte code. This allows Classpath Helper to merely report on missing class references instead of running into errors. A class that can not find its dependent classes cannot be properly loaded into the VM.