This notion is referred to as 'separation of powers'.
Over the years 'the Rule of Law' has gained many critical acclaims due to the traditional ethical values it uphold in the UK constitution. Those set of values are universally accepted and implemented in most of the European states for the rule does not allow any deviation or updation in the 'written' or 'unwritten' part of the Constitution.
'Separation of powers' the word created by a French thinker 1 is today pursued by the doctrine of the separation of powers (SOP) which suggests that SOP is no less important globally than nationally. This refers to the fundamental commitment to the creation and maintenance of independent judicial bodies to interpret and apply diverse areas of international law is essential to international law's continuing integrity 2.
SOP refers to that established constitutional principle that believes and negates the notion that, there must not be any accumulation of too much power in a single entity (one person) or decision-making body, instead the power must be distributed among the three branches of the constitution named the Executive, the Legislature and the Judiciary. In case the power is vested in a single authority, it would lead to inefficiency and corruption 3.
Lord Scarman invoked Entick v. ...
The King's messengers were liable for trespass in the absence of authority indicating the legality of general warrants of search and seizure: the 'silence of the books' was held to be authority against them. The House of Lords held that a constable could not lawfully require a person to provide a breath specimen, under the Road Traffic Act 1972, section 8, if he were present on that person's property without permission. Police officers had not been acting in the execution of their duty, as was necessary for a valid exercise of the power, because they were trespassers 4.
The Rule of Law indicated in this case provides the foundation of constitutional rights. The legality of the issue and execution of general warrants of search and seizure could not be established, and the King's Messengers were therefore liable for trespass. The judges would see if justification were provided by statute or common law: 'If no such excuse can be found or produced, the silence of the books is an authority against the defendant 5.
McGonnell V. UK
McGonnell v UK case depicts the violation in the context of separation of power, which the court found guilty of regarding the lack of prejudice in requirement in Article 6(1). "This was mainly because of the personal relations between the judiciary of the Bailiff of Guernsey and his legislative and executive roles. The Bailiff's overlapping functions meant that he had presided over the Guernsey legislature when it had adopted the Development Plan, which was relevant to the applicant's planning application. The Bailiff's attitude in his judicial capacity made clear to the court the applicant's planning appeal, therefore the Court held this to be in breach