The First Constituent Congress declared itself installed on 29 March in Mexico City, being supported by the provincial deputations—each composed of a political chief and an intendant—on the condition that a new Congress be convened following the precepts of the Plan of Casa Mata. On 31 March, the Congress issued three decrees: the first abolished the imperial Executive Power, which had been in operation since 19 May 1822 through the
Regency; the second established that a collegiate body called the
Supreme Executive Power would be appointed, composed of three members who would alternate its presidency; As the first two were not present in the capital at the time, the following day
José Mariano Michelena and
José Miguel Domínguez were appointed as substitutes while the members of the triumvirate were unavailable. was appointed as sole minister in charge of all the secretariats of state. After the Emperor restored Congress on April 7, it concentrated on dealing with the abdication of Iturbide. The abdication was not officially recognized, as Iturbide's election was declared to have been forced upon congress by threat of violence, and hence the throne was not legally his in the first place. The debates in congress over this matter became very heated. When a deputy attempted to declare that his vote for the emperor, representing the wishes of his district, had been free and uncompelled, the chamber rose in hostile uproar. Iturbide's coronation, titles of nobility, and hereditary succession were declared null and void. The Supreme Executive Power was asked to expedite the departure from the country of the former Emperor, who was granted an annual pension of 25,000 pesos on the condition that he would leave the country. Despite the controversy, the Plan of Iguala and the Treaty of Córdoba which had established the empire, were declared null and void. On May 11, escorted by Nicolás Bravo, and supervised in his embarkation by Guadalupe Victoria at
La Antigua, Iturbide and his family left the country on the British merchant frigate
Rowllins, with
Livorno as his destination. Upon Bravo's return to the capital, the Executive named new ministers:
Lucas Alamán to Interior and Exterior Relations,
Francisco de Arrillaga to the Treasury,
Pablo de La Llave to Justice and Ecclesiastical Affairs, and to War and Marine. Political prisoners were liberated, Iturbide's council of state was abolished, and a new Supreme Court was established. On 16 May 1823, from
San Agustín de las Cuevas,
Vicente Guerrero issued a manifesto to his compatriots reaffirming his opposition to the imperial regime and calling for national unity. Finally, due to the absence of Guadalupe Victoria, Guerrero was appointed substitute member of the Supreme Executive Power. On 21 May, the call was issued to form the new Congress. On 23 June, the provisional structure of the Supreme Court of Justice was established, composed of three chambers. On 19 July, Congress issued the decree declaring “good and meritorious the services rendered to the nation in the first eleven years of the war of independence and eminently meritorious in a heroic degree” to
Miguel Hidalgo,
Ignacio Allende,
Juan Aldama,
Mariano Abasolo,
José María Morelos,
Mariano Matamoros,
Leonardo and
Miguel Bravo,
Hermenegildo Galeana,
José Mariano Jiménez,
Xavier Mina,
Pedro Moreno, and
Víctor Rosales. Their names were ordered to be inscribed in gold letters in the Congress hall, and commemorative monuments were to be erected at the places where they were executed. Their remains were exhumed so that on 16 September 1823 they could be transferred from distant locations to the
Mexico City Cathedral. On 29 August,
Guadalupe Victoria and
Vicente Guerrero were likewise declared meritorious of the nation. On 11 September,
Benedicto López was declared meritorious, and a pension was granted to his widow. On 3 October 1823, the Treaty of Union, League, and Perpetual Confederation between Colombia and Mexico was signed. On July 19, 1823, Congress honored 11 deceased heroes who had fought for Mexican independence:
Miguel Hidalgo,
Ignacio Allende,
Juan Aldama,
Mariano Abasolo,
José María Morelos,
Mariano Matamoros, ,
Leonardo Bravo,
Galeana,
Jiménez,
Mina,
Pedro Moreno, and
Rosales. Their names were ordered to be inscribed in gold over the congressional chamber, and monuments were ordered to be raised in their places of death. The remains which could be found were exhumed in order to hold a state funeral for them. In the aftermath of the ceremonies, a mob plotted to visit the tomb of
Hernán Cortés in order to desecrate his bones, and the government had to send for the remains to be hidden and protected. The political opposition to Iturbide at this time also led to a change in the commemoration of Mexican Independence. The War of Mexican Independence went through multiple phases, not at all under the same leadership or with the same aims, and in 1821, it was Iturbide who had finally gained independence from Spain, leading to a commemoration of the matter on the anniversary of his army's entrance into Mexico City on September 27. However, with the fall of Iturbide, the commemoration of independence was moved to September 16, commemorating the
Cry of Dolores that had begun the struggle for independence. == Administrative measures ==