Coke's changed position from Attorney General to Chief Justice allowed him to openly attack organisations he had previously supported.
His first target was the Court of High Commission, an ecclesiastical court established by the monarch with near unlimited power; it administered a mandatory ex officio oath that deliberately trapped people.
The High Commission was vastly unpopular among both common lawyers and Members of Parliament, as the idea of "prerogative law" challenged both authorities.
The appointment of Richard Bancroft as Archbishop of Canterbury in 1604 caused the issue to grow in importance; according to P.B. Waite, a Canadian historian, Bancroft's zeal and strictness "could hardly fail to produce an atmosphere in which principles and issues would crystallize, in which logic would supplant reasonableness".
The judges, particularly Coke, began to unite with Parliament in challenging the High Commission.
 In 1607 Parliament openly asked for Coke's opinion on the High Commission's practices; he replied that "No man ecclesiastical or temporal shall be examined upon secret thoughts of his heart or of his secret opinion".

During this period a "notorious suit" ran through the courts, known as Fuller's Case after the defendant, Nicholas Fuller.
A barrister, Fuller had several clients fined by the High Commission for non-conformity, and stated that the High Commission's procedure was "popish, under jurisdiction not of Christ but of anti-Christ".
For this, Fuller was held in custody for contempt of court.
The Court of King's Bench argued that this was a lay matter, while the High Commission claimed it fell under their jurisdiction.
Coke had no official role, other than acting as a mediator between the two, but in the end Fuller was convicted by the High Commission.
This was a defeat for the common law, and in response Coke spent the summer issuing writs of prohibition to again challenge Bancroft and the High Commission.
On 6 November 1608, the common law judges and members of the High Commission were summoned before the king and told that they would argue and allow him to decide.
Finding themselves unable to even argue coherently, instead "[standing] sullen, merely denying each others' statements", the group was dismissed and reconvened a week later.
Coke, speaking for the judges, argued that the jurisdiction of the ecclesiastical courts was limited to cases where no temporal matters were involved and the rest left to the common law.

At this point the King's own position in relation to the law, and his authority to decide this matter, was brought up, in what became known as the Case of Prohibitions.
James stated that "In cases where there is not express authority in law, the King may himself decide in his royal person; the Judges are but delegates of the King".
Coke challenged this, saying "the King in his own person cannot adjudge any case, either criminal – as treason, felony etc, or betwixt party and party; but this ought to be determined and adjudged in some court of justice, according to the Law and Custom of England".
Coke further stated that "The common law protecteth the King", to which James replied "The King protecteth the law, and not the law the King!
The King maketh judges and bishops.
If the judges interpret the laws themselves and suffer none else to interpret, they may easily make, of the laws, shipmen's hose!".
Coke rejected this, stating that while the monarch was not subject to any individual, he was subject to the law.
Until he had gained sufficient knowledge of the law, he had no right to interpret it; he pointed out that such knowledge "demanded mastery of an artificial reason ... which requires long study and experience, before that a man can attain to the cognizance of it".
Coke was only saved from imprisonment by Cecil, who pleaded with the King to show leniency, which he granted.
After the conclusion of this dispute, Coke freely left, and continued to issue writs of prohibition against the High Commission.
Coke's changed position from Attorney General to Chief Justice allowed him to openly attack organisations he had previously supported. His first target was the Court of High Commission, an ecclesiastical court established by the monarch with near unlimited power; it administered a mandatory ex officio oath that deliberately trapped people. The High Commission was vastly unpopular among both common lawyers and Members of Parliament, as the idea of "prerogative law" challenged both authorities. The appointment of Richard Bancroft as Archbishop of Canterbury in 1604 caused the issue to grow in importance; according to P.B. Waite, a Canadian historian, Bancroft's zeal and strictness "could hardly fail to produce an atmosphere in which principles and issues would crystallize, in which logic would supplant reasonableness". The judges, particularly Coke, began to unite with Parliament in challenging the High Commission.  In 1607 Parliament openly asked for Coke's opinion on the High Commission's practices; he replied that "No man ecclesiastical or temporal shall be examined upon secret thoughts of his heart or of his secret opinion".
During this period a "notorious suit" ran through the courts, known as Fuller's Case after the defendant, Nicholas Fuller. A barrister, Fuller had several clients fined by the High Commission for non-conformity, and stated that the High Commission's procedure was "popish, under jurisdiction not of Christ but of anti-Christ". For this, Fuller was held in custody for contempt of court. The Court of King's Bench argued that this was a lay matter, while the High Commission claimed it fell under their jurisdiction. Coke had no official role, other than acting as a mediator between the two, but in the end Fuller was convicted by the High Commission. This was a defeat for the common law, and in response Coke spent the summer issuing writs of prohibition to again challenge Bancroft and the High Commission. On 6 November 1608, the common law judges and members of the High Commission were summoned before the king and told that they would argue and allow him to decide. Finding themselves unable to even argue coherently, instead "[standing] sullen, merely denying each others' statements", the group was dismissed and reconvened a week later. Coke, speaking for the judges, argued that the jurisdiction of the ecclesiastical courts was limited to cases where no temporal matters were involved and the rest left to the common law.
At this point the King's own position in relation to the law, and his authority to decide this matter, was brought up, in what became known as the Case of Prohibitions. James stated that "In cases where there is not express authority in law, the King may himself decide in his royal person; the Judges are but delegates of the King". Coke challenged this, saying "the King in his own person cannot adjudge any case, either criminal – as treason, felony etc, or betwixt party and party; but this ought to be determined and adjudged in some court of justice, according to the Law and Custom of England". Coke further stated that "The common law protecteth the King", to which James replied "The King protecteth the law, and not the law the King! The King maketh judges and bishops. If the judges interpret the laws themselves and suffer none else to interpret, they may easily make, of the laws, shipmen's hose!". Coke rejected this, stating that while the monarch was not subject to any individual, he was subject to the law. Until he had gained sufficient knowledge of the law, he had no right to interpret it; he pointed out that such knowledge "demanded mastery of an artificial reason ... which requires long study and experience, before that a man can attain to the cognizance of it". Coke was only saved from imprisonment by Cecil, who pleaded with the King to show leniency, which he granted. After the conclusion of this dispute, Coke freely left, and continued to issue writs of prohibition against the High Commission.
Edward Coke