Why was the rule about criminous clerks the most controversial part of the Constitutions of Clarendon?

The provision regarding "criminous clerks" (clause 3) was the most controversial part of the Constitutions of Clarendon because it fundamentally challenged the church’s judicial autonomy and its long-standing privilege of benefit of clergy.12

Historically, clerics accused of crimes were tried in ecclesiastical courts, where they were often subject to more lenient punishments—such as degradation or exile—rather than the death or mutilation typically imposed by secular courts. King Henry II sought to restrict these privileges, arguing that clerical crime was widespread and encouraged by the lack of severe penalties.12

Thomas Becket, as Archbishop of Canterbury, fiercely opposed this provision. He argued that subjecting a clerk to secular punishment after they had already been judged by the church violated the principle of "not twice for the same fault" (double jeopardy). This clash represented a deeper struggle between royal authority and the canon law of the church, ultimately leading to Becket's exile and martyrdom.21