Jeremy Waldron has an interesting article on The Rule of Law at the SEP. The section on Albert Venn Dicey seems to me to be very misleading, however: Waldron says, "For Dicey, the key to the Rule of Law was legal equality," but while legal equality is important, I think it is not the key to Dicey's understanding of the idea of the rule of law.
What Dicey tells us is that there are actually three 'kindred' notions that are involved when we talk about 'rule of law':
(1) Security from arbitrary governmental power: This is the 'first principle of the Rule of Law' that Waldron quotes, "no man is punishable or can be lawfully made to suffer in body or goods except for a distinct breach of law established in the ordinary legal manner before the ordinary Courts of the land".
(2) Equality before the law: This is what Waldron says is key to his account, namely, that "every man, whatever be his rank or condition, is subject to the ordinary law of the realm and amenable to the jurisdiction of the ordinary tribunals." Waldron's objection is irrelevant here; officials are not 'above the law', and they are not exempted from the ordinary law of the realm. If we say, as Waldron does, that officials "need to be hemmed in by extra restrictions" then if the restrictions are extra, they obviously are not exemptions from being subject to the law of the realm; and where are these restrictions coming from? If they arise from the ordinary legal means of ordinary tribunals, then this is precisely the kind of thing Dicey means. If you think that you need special courts for officials, or a special law governing officials only, the problems that immediately arise are (a) conflicts of jurisdiction in dealing with problems arising from the relations between officials and non-officials; (b) how is this not to say that one of the two groups, officials or non-officials, is a second-class citizenry, if they do not have the same protections for their rights and freedoms as everyone else?
[Note that Dicey's understanding of the rule of law in this second sense does not automatically generate a presumption of liberty, because Dicey specifically formulates his account of 'rule of law' so that it is consistent with a very, very strong view of parliamentary sovereignty (Parliament, understood as Crown, House of Lords, and House of Commons in cooperation, without restriction or limitation may make or unmake any law whatsoever, and the laws of Parliament may not be set aside by anything other than Parliament itself). Liberty is not what Dicey primarily has in mind when he is talking about rule of law.]
(3) Organic constitution: The constitutional law is not the source of but the consequence of the rights of individuals, as defined by courts; that is to say, "the constitution is the result of the ordinary law of the land." As Dicey points out in an example later on, English freedom is not guaranteed by a proposition in a document; freedom of person is not a privilege to be guaranteed at all -- it is the outcome of the ordinary law of the land as applied by courts. The Englishman's rights are built into the system, and require no paper guarantee or special intervention.
Dicey occasionally treats these as three perspectives on one thing (when he is talking about English law, usually), but more commonly treats them as distinct but related elements. Note that in all three cases the key concept is not 'equal' but 'ordinary'. Rule of law is, at a crude, vague level, about the primacy of ordinary law arising out of ordinary tribunals in an ordinary legal system. All three are ways in which one might recognize the supremacy of the ordinary law of the realm. If we look at droit administrif, one of the things this conception opposes, we find two ideas alien to English 'rule of law':
(1) That officials of the state have special privileges beyond those of ordinary citizens simply by being officials.
(2) Government should be structured by a separation of powers, which guarantees that other powers in the government are independent of the ordinary course of law as applied by courts.
Dicey's big idea with regard to rule of law is that the fundamental structure of government arises out of a normal course of law concerned with standard and stable protections for citizens, simply as citizens. He regards this as being, essentially, the power of courts to penalize any illegal activity, regardless of who has done it. This he sees as almost exclusively found in England (of his day), although he thinks that in practice the United States was also at least in the vicinity, despite its written constitution, because of judicial review.
It is possible that Dicey's view of rule of law is somewhat extravagant, as Waldron notes critics have often suggested, but it has more structure to it than you would get from Waldron's summary.