Thomas Becket and Isabelle de Warenne's dispute stemmed from Becket, as Archbishop of Canterbury's, refusal to grant a dispensation for her to marry William X, Count of Poitou, who was King Henry II's younger brother.
Isabelle de Warenne was a wealthy heiress, having inherited the earldom of Surrey and her father's lands. After her first husband, William of Blois, died in 1159, she was sought in marriage by William X, Count of Poitou. However, Thomas Becket, as Archbishop of Canterbury, blocked the marriage in 1162 or 1163. The reason given was consanguinity, meaning the couple were too closely related. While they may not have been directly related, William X and Isabelle's first husband, William of Blois, were cousins.
Becket's refusal was a point of contention with King Henry II, as it prevented the de Warenne lands from being brought into the king's family through this marriage. After the refusal, William X died shortly after, which some anti-Becket propagandists of the time claimed was from a broken heart.
Following this, Isabelle de Warenne married Hamelin of Anjou, who was King Henry II's illegitimate half-brother, in April 1164. Hamelin took the name de Warenne and became Earl of Surrey.
Thomas Becket's canon law arguments against granting the dispensation for the marriage refusal were centred on the following principles:
Consanguinity and Impediments: According to canon law, marriages within certain degrees of blood relationship (consanguinity) were prohibited unless a dispensation was granted. Becket adhered strictly to these rules, believing that the law forbade marriage without papal dispensation when close kinship existed. He saw such impediments as integral to the Church's moral and juridical order that should not be overridden lightly.
Limits on Dispensation Powers: Though dispensations could be granted by the Pope or authorized church authorities for just and urgent causes, these dispensations were to be carefully regulated. Canon law forbade granting dispensations arbitrarily or without serious justification ("just and urgent cause"), especially for matrimonial impediments that could affect the sanctity of marriage and the Church's authority.
Ecclesiastical Authority and Jurisdiction: Becket upheld that only the Church had authority in matters of marriage law and morality. He rejected secular encroachments or pressure to grant dispensations contrary to Church law, asserting the supremacy of ecclesiastical jurisdiction over matrimonial issues.
Preservation of Church Law Integrity: Becket maintained that granting a dispensation without sufficient cause would undermine the integrity of canon law, weaken Church discipline, and could be considered illicit or invalid. He insisted that dispensations must not threaten the essential constitutive principles of marriage as a sacrament.
These canon law principles underpinned Becket's refusal to grant the dispensation for the marriage involving Isabel de Warenne, reflecting his commitment to uphold Church doctrine and resist royal interference in ecclesiastical matters.+2
Eleanor of Aquitaine was running the country at the time while Henry II was in France and she had used the argument of consanguity previously and reasonably recently to divorce her husband Louis VII, the king of France. It would have been quite hypocritical of Thomas Becket to have granted permission in this case. Nevertheless Becket proved himself capable of contradicting the royal wishes in matters of state and ecclesiastical law.
References
Isabel and Hamelin de Warenne: Marriage and Partnership – History… the interesting bits!
