The word arbitrary is derived from the Latin work arbitrarius, meaning the source of arbiter, who is the person who must judge a particular matter. In legal terms, an arbitrary judgment is a legal decision decided at the discretion of a judge, and is a decision that is not one that is fixed by law.
When a decision is arbitrary, it means that the decision is not based on judgment or reason but instead on discretion without any regard to standards or rules or personal will. It also implies a disregard of the evidence. In many circumstances, the term arbitrary implies an aspect of bad faith, and it sometimes may be taken as despotic or tyrannical.
https://court.laws.com/arbitrary
Extract from Concept of the Rule of Law in ECHR Case Law by Davit Melkonyan, Candidate of Legal Sciences, Docent ofthe Chair of Criminal Procedure and Criminalistics of the Yerevan State University, Head of the Department of Criminal Charge and Appelation of the General Prosecutor’s Office. E-mail:
Consequently, the law must indicate the scope of any such discretion conferred on the competent authorities and the manner of its exercise with sufficient clarity, having regard to the legitimate aim of the measure in question, to give the individual adequate protection against arbitrary interference”. 36
In the circumstances of the case, the Court concluded that “the minimum degree of legal protection to which citizens are entitled under the rule of law in a democratic society is lacking”.37
Whenever the interference is authorized by the judiciary, the rule of law requires the judges’ discretion to be confined within certain limits.38
The Court has applied the qualitative requirements of the law in many cases concerning interferences with the right to private and family
life.39
36 Malone v. United Kingdom, 2 August 1984, § 68.
37 Malone v. United Kingdom, § 79.
38 Kruslin and Huvig v. France, 24 April 1990.
39 Antunes
Rocha v. Portugal, 31 May 2005; Vetter v. France, 31 May 2005; Popescu v. Romania (n° 2), 26 April 2007; Hasan v. Bulgaria, 14 June 2007.
http://ysu.am/files/Davit_Melkonyan-1415702096-.pdf
And Yet….
Mr Justice Mostyn stated at p.40 SS v NS (Spousal Maintenance) [2014] EWHC 4183 (Fam)
“Since the advent of secular divorce in 1857 a decision about spousal maintenance has always been left by Parliament to the unfettered discretion of the individual judge:”
Also in Malone V UK
“the Court held that "a law which confers a discretion must indicate the scope of that discretion".