The author highlights the conflicting demands for certainty and fairness within Member State systems of procedural law. The obstacles to effective implementation of European law are particularly difficult to overcome when the need to maintain certainty in the law has high priority, as in the case of procedural laws. Nevertheless, differences in procedural laws are severely undermining the uniform application of European law in the Member States. The European Court has adopted the approach that national legal systems should have procedural autonomy to a large extent — limited by the need to ensure that Community law rights are not subject to less favourable procedural conditions than those applying in the case of domestic law rights and that it does not become "virtually impossible" for a litigant to assert his or her Community law rights. This approach is unsatisfactory. It does not adequately promote the effectiveness of Community law rights. An alternative theory has emerged in recent ECJ case law, in which the purpose of the national law rule is investigated to determine whether it is compatible with Community law. This approach is also problematic, however. It leads to a high degree of uncertaintyover the validity of national procedural laws. The ECJ should retain its approach based on procedural autonomy, but identify more precisely the particular problems that the case law is trying to resolve. In particular, the key cases are concerned with the inadequate transposition of Directives into national law. Rules specific to this problems should be put in place. The obstacles caused by procedural laws should then be monitored to allow further intervention by way of harmonisation to meet identifiable needs.