It is not a secret that taking an oath to become a the head of a republic or ministry, or any other significant position in a state, is considered a necessary step towards completing the protocols required for the new official to take over his new office, even when such official is directly elected, as it is the case with the American presidential system.
Therefore, provisions related to legal oath are stated in constitutions. It is customary, as per constitutional provisions, that the new official takes a legal or constitutional oath, as stated in the system adopted by the relevant country.
In addition, a constitutional oath should be taken before the new office holder commences his duties, based on a provision in the constitution or a followed constitutional custom. The constitutional oath is taken before the commission or authority to which the position to be held is affiliated: legislative, executive, or judiciary, as stated in the constitution. Constitutional oath is thus considered one of the modern ceremonies in parliaments. The new office holder – whether a president, minister, or any other official – is not permitted to start carrying out his duties unless he takes such oath. This oath requirement can also be found in non-governmental organizations and unions. For a lawyer, for instance, to practice his profession, he is required to take an oath before the bar’s council or a special court. This also applies for other types of unions.