In international law and international relations, a protocol is usually an international treaty or agreement that complements a previous treaty or international agreement. A protocol can modify the previous contract or add additional terms. The Contracting Parties to the previous Agreement are not obliged to accept the Protocol. Sometimes this is made clearer by calling it an “optional protocol,” especially when many parties to the first agreement do not support the protocol. Originally, international law did not accept treaty reservations and rejected them unless all parties accepted the same reservations. However, in order to encourage as many States as possible to accede to treaties, more permissive regulations on reservations had emerged. Although some treaties still expressly prohibit reservations, they are now generally permitted as long as they are not contrary to the objectives and purposes of the treaty. Bilateral treaties are concluded between two States or bodies.  It is possible for a bilateral treaty to have more than two parts; Thus, each of the bilateral agreements between Switzerland and the European Union (EU) has seventeen parts: the parties are divided into two groups, the Swiss (“on the one hand”) and the EU and its member states (“on the other hand”). The Treaty defines the rights and obligations between Switzerland and the EU and the Member States in a single context – it does not create rights and obligations between the EU and its Member States. [Citation required] An essential part of the treaty conception is that the signing of a treaty implies the recognition that the other party is a sovereign State and that the agreement in question is enforceable under international law. Therefore, nations can be very cautious when it comes to calling an agreement a treaty. .