Constitutional conventions are informal and uncodified traditions that are followed by the institutions of a state). They are rules of good political behavior that are typically rules of self-restraint, not exercising powers to the full. Constitutional conventions are at work across all branches of government—legislative, judicial, and executive. Each embodies a principle of responsible government, or self-restraint: not exercising legal powers to the full; not abusing public power; and respecting the constitutional role and functions of the other branches of government.

Constitutional conventions arise when the exercise of a certain type of power, which is not prohibited by law, arouses such opposition that it becomes impossible, on future occasions, to engage in further exercises of this power). Conventions are rules of the constitution that are not enforced by the law courts, but they regulate the working of the constitution and are an important concern of the constitutional lawyer).

Examples of constitutional conventions include the principle of responsible government, the principle of collective responsibility, the principle of ministerial accountability, and the principle of judicial independence. The Cabinet Manual sets out the main constitutional conventions, and the Ministerial Code the standards of conduct expected of ministers. Conventions have increasingly been codified in official guidance of this kind; a few conventions have even been codified in statute.

Constitutional conventions play a key role in the uncodified British constitution). They are rules that are observed by the various constituted parts though they are not written in any document having legal authority; there are often underlying enforcing principles that are themselves not formal and codified).