Constitutional law is concerned with the role and powers of the institutions within the state and with the relationship between the citizen and the state . Thus, it tends to concentrate on the relation between the primary organs of sovereign power (for example, Parliament and the judiciary) and the fundamental principles of constitutionalism, such as the rule of law. All constitutional law presupposes the existence of a constitution, whether written or not.
A constitution sets out the relationship between individuals and the Government. It is a document that sets out necessary rules for the framework and operation of state institutions, for example defining the powers of the state and its agencies. Who can do what and where the limits of power are. This can only be of value if people feel an ownership of their constitution and other institutions are open and fair.
Administrative Law
Administrative Law is the law that governs the actions of public authorities. According to well-established rules of administrative law, a public authority must possess the power to carry out what it intends to do. If not, its action will be ultra vires - i.e. beyond its lawful powers. For public authorities considering the lawfulness of any data-sharing they propose to undertake, a key question is therefore whether they have the power or vires to process personal data.
Public bodies need to have a statutory basis for data-sharing. In addition to the necessity for a power to exist, it is also necessary that the power must be exercised for the purpose for which it was created.
As well as the specific powers provided to public authorities, it is clear that they may also undertake tasks "reasonably incidental" to the defined purpose.
The UK constitution looks confusing to a foreign observer: most states have a written constitution which is a document with special sanctity; a declaration of the country's supreme law; all laws and all institutions of their state subordinate to a written constitution and intended to be an enduring statement of fundamental principles (See Bradley and Ewing; and Turpin). This is to describe a constitution narrowly. Yet even where there is a formal document, not all the rules are found there. However it is a good place to start.
UK constitution
If we made a complete list of all the multiple sources of rules and principles, i.e. legal rules (statute, common law) and non-legal rules (conventions) that would be put into a written constitution it might provide a single document but it would fail to reveal some important features. A wide definition is that a constitution is a body of legal and non-legal rules that establishes institutions, governs the relationship between them, and governs the relationship between the individual and the state. However a functional analysis is inadequate, it is too dry. A constitution must also embody a nation's values; it must be directed to the public good, give people a reason for action, give people a stake in the ...