1) Direct effect allows EU law to confer rights on individuals that can be enforced in national courts. This was established in the 1963 case Van Gend en Loos, where the ECJ found that article 30 of the Treaty of Rome had direct effect.
2) For a provision to have direct effect, it must be clear and unconditional, conferring identifiable rights. Directives only have vertical direct effect against member states, while regulations can have both vertical and horizontal direct effect.
3) Indirect effect means that national law must be interpreted in line with EU law. This allows individuals to rely on unimplemented directives in national courts through purposive interpretation.
4) Member states can be liable to compensate individuals