derives from the fact that the decisions of the EDRB are specified to be not subject to subsequent review or modification by any other body. 249. The fact that an EDRB belongs to the judicial branch, in which there are higher-ranking bodies such as the Supreme Court, does not mean that it has to answer to a higher-ranking court. Nor does the possibility of its decisions being subject to review, overturned or amended mean that its functional independence is lost or limited. The relevant consideration is that the EDRB should be subject only to its mandate as set out in the constitution and the law when ruling on the merits of the challenges filed. 250. In general, it may be considered good practice to entrust an EDR system to permanent and independent bodies. When electoral laws provide EDRBs with mandates that do not authorize them to continue to operate beyond the electoral period, other bodies must be entrusted with resolving any possible challenges that arise during the pre-electoral and post-electoral periods. While arguments about the overall priorities for use of scarce human and financial resources are important, they need to be set against the potential costs arising from lower credibility in resolving electoral disputes which arise outside the electoral period itself. 251. Several countries vest an important power to develop and adopt regulations under a country’s electoral law in the supreme body of an EDRS which takes the form of special electoral courts. Some electoral courts are authorized to issue by-laws, as for example in Mexico. This power can also be given to an EMB with the authority to resolve electoral disputes, which is the case in the Dominican Republic, El Salvador, Gambia, Uruguay and Yemen. 252. In addition, some countries give EDRBs the power to initiate electoral legislation, for example, Ecuador and Peru. Others establish an obligation to consider the opinion of the EDRB in the legislative process relating to electoral issues, as in Costa Rica where a two-thirds majority of the legislature is required before it can go against the opinion of the Supreme Elections Tribunal. 253. Some EDR systems also empower the highest-level court in the EDR system to establish binding judicial precedent through case law. The Superior Chamber of the Electoral Court of the Judicial Branch of the Federation in Mexico does so when it reiterates the same view in three consecutive cases, or when it resolves the conflicting views of two regional chambers, or of one regional chamber and the Superior Chamber, and determines the criteria that should prevail. This case law is binding in future cases, not only on the lower EDRBs but also on the EMB. This is common practice in judicial systems, particularly in common law countries that have the stare decisis doctrine. However, some countries with a civil law tradition, such as El Salvador, do not allow binding case law. 92