1. The lack of rules or law, which leads to ad-hoc and inconsistent adjudication.
2. Failure to publicize or make known the rules of law.
3. Unclear or obscure legislation that is impossible to understand.
4. Retroactive legislation.
5. Contradictions in the law.
6. Demands that are beyond the power of the subjects and the ruled.
7. Unstable legislation (ex. daily revisions of laws).
8. Divergence between adjudication/administration and legislation.

Fuller presents these problems in his book The Morality of Law with an entertaining story about an imaginary king named Rex who attempts to rule but finds he is unable to do so in any meaningful way when any of these conditions are not met. Fuller contends that the purpose of law is to "subject human conduct to the governance of rules". Each of the 8 features which lead to failure form a corresponding principle to avoid such deficiencies which should be respected in legislation. If any of these 8 principles is not present in a system of governance, a system will not be a legal one. The more closely a system is able to adhere to them, the nearer it will be to the ideal, though in reality all systems must make compromises. These principles, Fuller argues, represent the "internal morality of law", and he argues that compliance with them leads to substantively just laws and away from evil ones.

In his review of "The Morality of Law" Hart criticises Fuller's work, saying that these principles are merely ones of efficacy; it is inept, he says, to call them a morality. One could just as well have an inner morality of poisoning as an inner morality of law, but of course we find this idea absurd. A contemporary debate rages, with much "bombast and invective" (Kramer, "Big Bad Wolf", (2005)), between Professor Matthew Kramer and Dr. Nigel Simmonds over the moral value of the rule of law as constituted by Fuller's 8 principles. The former agrees with Hart that it is compatible with great iniquity, arguing that evil regimes would have good prudential reasons for complying with it. The latter contends that adhering to the rule of law has value in and of itself, giving citizens a liberty to act as they please and conform their conduct to the rules and know that if they do so force beyond that which is prescribed will not be used against them by the state. Evil regimes would have every reason to operate outside the rule of law to 'chill' the population into compliance, rather than to use the rule of law for their own ends as Kramer suggests.