A general law, rule, principle, or criterion by which something is judged:
All they have is administrative fiat which fails any of the canons of the rule of law.
Since the definitions explains 'canon' with 'rule', I think 'the canons of the rule of law' is just redundancy and it should be just 'the rule of law'.
You may refer to the meaning of 'the rule of law' on http://www.ldoceonline.com/dictionary/rule_1 Definition#6
Not a teacher.
"Canon" can be a principle or a standard that is the basis for a law.
Pope of the Dictionary.com Forum