According to Roman Catholicism, was the 1054 excommunication of the Patriarch of Constantinople valid, in light of Leo IX's death? The excommunications of 1054 have long been seen as a pivotal moment in the Great Schism.  But recently I found that some people apparently doubt that the excommunication of the Patriarch of Constantinople was actually valid, because the pope that had sent the representatives, Leo IX, had already died when the excommunication was announced.  The linked Wikipedia article calls its validity "doubtful," while a different article, this time without a source, simply says that because Leo IX had died, "the excommunication was thereby invalid."  

Yet I also know that in 1965, Pope Paul VI lifted the 1054 excommunication – which seems to suggest that it was valid.  And Everett Ferguson (Church History, I, 19.V.B) gives no indication of their invalidity.

According to Roman Catholicism, then, was the excommunication of the Patriarch valid?  Were the representatives able to validly excommunicate only until Leo IX's death, or only until his successor took office, or anytime?
According to Roman Catholicism, was the 1054 excommunication of the Patriarch of Constantinople valid, in light of Leo IX's death?

The short answer is no.

Even in the seminary, all my professors said that the excommunication imposed by the Cardinal Humbert of Silva Candida’s day was is invalid because at the moment he pronounced the above said excommunication, Pope Leo IX had already died. Tradition holds that Cardinal Humbert never lost his title of legal standing as a papal legate of Pope Leo upon the death of this same pope.


  Since the jurisdiction of a legate is ordinary, he does not cease to be legate even at the death of the pope who appointed him, and even if he arrived at his post after the death of that pope. - Legate (Catholic Encyclopædia)


Now here is  major problem with Cardinal Humbert’s actions. Only the Supreme Pontiff may excommunicate bishops and sovereigns. Although legate may excommunicate someone in the name of a Sovereign Pontiff, Legate Humbert could not pronounce such a sentence as Pope Leo IX had been dead for three months.

Only the Pope can excommunicate bishops because only he has jurisdiction over them. Pope Leo IX died on April 19,1054 and Cardinal Humbert’s excommunication was executed on the 16th of July, 1054. Although he retained the office of legate after the Pontiff’s death, he lost the ability to excommunicate him in the name of the pope because the Holy See was in a state of sede vacante.


  In a certain sense excommunications may also be reserved in view of the persons who incur them; thus absolution from excommunications in foro externo incurred by bishops is reserved to the pope; again, custom reserves to him the excommunication of sovereigns. - Excommunication (Catholic Encyclopædia)


Thus it is not the fact that he was or was not the legitimate papal legate at that moment in time. It is a fact that he could not excommunicate a bishop in the pope’s name since Pope Leo was dead.

Now let us look at the evidence, if any, more closely.


  Mutual excommunication of 1054
  
  In 1053 Leo of Ohrid, at the instigation, according to J. B. Bury, of Patriarch Michael Cerularius of Constantinople, wrote to Bishop John of Trani a letter, intended for all the Latin bishops, including the pope, in which he attacked Western practices such as using unleavened bread for the Eucharist, and fasting rules that differed from those in Constantinople, while Cerularius himself closed all Latin churches in Constantinople.
  
  In response, Leo IX wrote the letter In terra pax of 2 September 1053, addressed to Cerularius and Leo of Ohrid, in which he speaks at length of the privileges granted through Saint Peter to the see of Rome. In one of the 41 sections of his letter he also speaks of privileges granted by the emperors, quoting from the Donation of Constantine document, which he believed to be genuine (section 20). Some scholars say that this letter was never actually dispatched, but was set aside, and that the papal reply actually sent was the softer but still harsh letter Scripta tuae of January 1054.
  
  The advance of the Norman conquest of southern Italy constituted a threat to the possessions of both the Byzantine Empire and the papacy, each of which sought the support of the other. Accordingly, conciliatory letters, the texts of which have not been preserved, were written to the pope by the emperor and Cerularius. In his January 1054 reply to the emperor, Quantas gratias, Leo IX asks for his assistance against the Normans and complains of what the pope saw as Caerularius's arrogance. In his reply to Caerularius, he upbraided the patriarch for trying to subject the patriarchs of Alexandria and Antioch to himself and for adopting the title of Ecumenical Patriarch, and insisted on the primacy of the see of Rome.
  
  These two letters were entrusted to a delegation of three legates, headed by the undiplomatic cardinal Humbert of Silva Candida, and also including Frederick of Lorraine, who was papal secretary and Cardinal-Deacon of Santa Maria in Domnica, and Peter, Archbishop of Amalfi. They were given friendship and support by the emperor but were spurned by the patriarch. Finally, on 16 July 1054, three months after Pope Leo's death in April 1054 and nine months before the next pope took office, they laid on the altar of Hagia Sophia, which was prepared for celebration of the Divine Liturgy, a bull of excommunication of Cerularius and his supporters. At a synod held on 20 July 1054, Cerularius in turn excommunicated the legates. In reality, only Michael may have been excommunicated along with his then-living adherents.
  
  At the time of the excommunications, many contemporary historians, including Byzantine chroniclers, did not consider the event significant.
  
  Efforts were made in subsequent centuries by emperors, popes and patriarchs to heal the rift between the churches. However, a number of factors and historical events worked to widen the separation over time.
  
  "Even after 1054 friendly relations between East and West continued. The two parts of Christendom were not yet conscious of a great gulf of separation between them. … The dispute remained something of which ordinary Christians in East and West were largely unaware".
  
  There was no single event that marked the breakdown. Rather, the two churches slid into and out of schism over a period of several centuries, punctuated with temporary reconciliations. - East–West Schism


Cardinal Humbert acted with impunity when in the presence of the Patriarch of Constantinople to say the least. Having known the pope had died, a papal legate’s authority was seriously diminished and he knew that. Cardinal Humbert deserved to be excommunicated himself for the actions he chose to do!


  Pope Leo IX sent an official delegation on a legatine mission to treat with the Patriarch. Members of the papal delegation were: cardinal Humbert of Silva Candida, papal secretary Frederick of Lorraine, who was Cardinal-Deacon of Santa Maria in Domnica, and Peter, Archbishop of Amalfi. Soon upon their arrival in Constantinople, news were received that pope Leo IX had died on 19 April. Since official position and authority of papal legates was dependent upon the pope who authorized them to represent him, the news of Leo's death placed his envoys in an awkward position. In spite of that, they decided to proceed with their mission, but even before any religious discussions were held, problems arose regarding some basic formalities and ceremonies. During the initial audience, Patriarch refused to meet with papal envoys in their official capacity and left them waiting with no further audience for months.
  
  During that time, from April to July 1054, cardinal Humbert and his colleagues continued with their activities in Constantinople, taking part in informal religious discussions on various issues. Their behavior was seen as inappropriate by the Patriarch. Despite the fact that their legatine authority officially ceased after popes death, cardinal Humbert and his colleagues decided to engage in open confrontation with the Patriarch. On Saturday, 16 July 1054, they produced a Charter of Excommunication (lat. charta excommunicationis), directed against Patriarch Michael of Constantinople, Archbishop Leo of Ohrid, and all of their followers. On the same day, cardinal Humbert and his colleagues entered the church of the Hagia Sophia during the divine liturgy and placed the Charter on the altar.
  
  Soon after that, Patriarch decided to react. On 20 July 1054, a synod of 21 metropolitans and bishops was held in Constantinople, presided by Cerularius. The council decided to excommunicate cardinal Humbert and his colleagues. Only the three men were anathematized, and a general reference was made to all who support them, but there was no explicit excommunication of the entire Western Christianity, or the Church of Rome. On Sunday 24 July the conciliar anathema was officially proclaimed in the Hagia Sophia Church.
  
  The events of 1054 caused the Great Schism and led to the end of the alliance between the Emperor and the Papacy, and caused later Popes to ally with the Normans against the Empire. Patriarch Michael closed the Latin churches in his area, which exacerbated the schism. In 1965, those excommunications were rescinded by Pope Paul VI and Patriarch Athenagoras, when they met in Jerusalem. Although the excommunication delivered by Cardinal Humbert was invalid, this gesture represented a significant step towards restoring communion between Rome and Constantinople.
  
  The short reign of the Empress Theodora saw Michael intrigue against the throne. Michael Psellus notes that while their initial relations had been cordial, once Theodora took the Imperial throne, they entered into open conflict, as Michael "was vexed because the Roman Empire was being governed by a woman", and on this topic "he spoke his mind freely.". The historian suggests that Theodora would have deposed Michael for his open effrontery and sedition, had she lived longer.
  
  Cerularius had a hand in negotiating the abdication of Michael VI Stratiotikos, convincing him to step down on 31 August 1057, in favour of the rebellious general Isaac, for whom the army declared on 8 June. The emperor duly followed the patriarch's advice and became a monk. Having had a role in bringing him to the throne, Cerularius next quarrelled with Isaac I Komnenos over confiscation of church property. Michael went so far as to take the highly symbolic step of donning the purple shoes ceremonially reserved for the Emperor. Michael apparently planned a rebellion, to overthrow the Emperor and claim the Imperial Throne for himself or for his relative Constantine Doukas. Isaac exiled Michael to Proconnesus in 1058 and, as Michael refused to step down, had Psellus drew up the Accusation of heresy and treason against him. Cerularius died before coming to trial. - Michael I Cerularius (Wikipedia)


Did Rome have the right to excommunicate Cerularius?


  The question about whether Rome should have excommunicated Cerularius is a good one. Pope Paul VI thought not, given the choice of words for the mutual 1965 statement. We don't think an excummunication should have happened. There probably was a better way to handle the mess. However, the question about whether the Pope had the right to do it is an entirely different matter, because it calls into question the right of Rome to intervene in matters of extreme importance to the entire Church. It also challenges the primacy of the seat of Peter.
  
  The Byzantine fathers affirm that Rome has the right and the duty to excommunicate heretics and schismatics. For example, St. Maximos the Confessor writes:
  
  
    “If the Roman See recognizes Pyrrhus to be not only a reprobate but a heretic, it is certainly plain that everyone who anathematizes those who have rejected Pyrrhus also anathematizes the See of Rome, that is, he anathematizes the Catholic Church.  I need hardly add that he excommunicates himself also, if indeed he is in communion with the Roman See and the Catholic Church of God ...Let him hasten before all things to satisfy the Roman See, for if it is satisfied, all will agree in calling him pious and orthodox.  For he only speaks in vain who thinks he ought to pursuade or entrap persons like myself, and does not satisfy and implore the blessed Pope of the most holy Catholic Church of the Romans, that is, the Apostolic See, which is from the incarnate of the Son of God Himself, and also all the holy synods, accodring to the holy canons and definitions has received universal and surpreme dominion, authority, and power of binding and loosing over all the holy churches of God throughout the whole world."  (Maximus, Letter to Peter, in Mansi x, 692). 
  
  
  This is a Byzantine forefather –a SAINT of the Orthodox Church.  
  
  It was not Rome’s authority to do so, he had not the office to be able to excommunicate. It is as unlawful  and silly as if a child were to cast his parents out of their own house.
  
  The Acts of the Council of Chalcedon, where over 500 Eastern bishops address Pope Leo the Great and declare:
  
  
    “Knowing that every success of the children rebounds to the parents, we therefore beg you to honor our decision by your assent, and as we have yielded agreement to the Head in noble things, so may the Head (Pope) also fulfill what is fitting for the children (other bishops)." --Chalcedon to Pope Leo, Ep. 98.
    
    "Wherefore the most holy and blessed Leo, archbishop of the great and elder Rome, through us, and through this present most holy synod together with the thrice-blessed and all-glorious Peter the Apostle, who is the Rock and foundation of the Catholic Church, and the foundation of the orthodox faith, hath stripped him (i.e., PATRIARCH Dioscorus of Alexandria) of his episcopate, and hath alienated from him all hieratic worthiness" --Acts of Chalcedon, Session 3. 
  
  
  According to the Ecumenical Council of Chalecedon, a Pope of Rome has the right and the power to excommunicate a patriarch (in this case, the Patriarch of Alexandria). So, the position that there was no right of excumminication is not only at odds with the fathers, but with the formal decree of an ECUMENICAL COUNCIL (Chalcedon), which recognizes the Pope of Rome’s authority to excommunicate a patriarch. This same canon of Chalcedon also says that Peter is the Rock of the Church. The idea of no right to excommunication is at odds with the fathers of this Ecumenical Council that Eastern Orthodoxy claims to accept and to be bound by.  
  
  Was the excommunication against the whole Eastern Church?
  
  Rome excommunicated Patriarch Michael Cerularius of Constantinople and all of his immediate clergy. It did not excommunicate the emperor, or the patriarchs of Alexandria, Antioch, or Jerusalem, or the bishops of any of the other Eastern churches (especially not in the Slavonic north or Russia). Nor did the Slavs or any of the other patriarchs ever excommunicate Rome. So, strictly speaking, Romans are still technically in communion with most of the Eastern Orthodox Church. And this is especially true because we formally healed the schism at Lyon II in 1274 and at Ferrara-Florence in 1439. Our present schism dates from 1472, when the Greeks renounced the union of Ferraea-Florence -- something the Slavic Churches never formally did. Also, in 1965, Patriarch Atheneagorus of Constantinople and Pope Paul VI nullified the excommunications from 1472, which means that Romans are now technically in communion with Constantinople itself though most Greeks do not recognize this. But, technically, there is no reason why we should not be in full communion today. 


More information may be gleaned from the following article(s):

Joint Catholic-Orthodox Declaration of His Holiness Pope Paul VI and the Ecumenical Patriarch Athenagoras I (December 7, 1965)