Editing Legality (section)

== Other related concepts ==
[[Rule of law]] provides for availability of rules, laws and legal mechanism to implement them. Principle of legality checks for availability and quality of the laws. Legality checks for if certain behaviour is according to law or not. concept of Legitimacy of law looks for fairness or acceptability of fairness of process of implementation of law.

The quality of being legal and observance to the law may pertain to lawfulness, i.e. being consistent to the law or it may get discussed in principle of legality or may be discussed as legal [[legitimacy (political)|legitimacy]].

===Legality of purpose===
In [[contract law]], legality of purpose is required of every enforceable contract. One can not validate or enforce a contract to do activity with unlawful purpose.<ref>{{cite web|url=https://www.law.cornell.edu/wex/example/%5Bfield_short_title-raw%5D_26|title=Legality of purpose – contracts|first=Michael|last=Litvin|date=15 September 2009|work=cornell.edu}}</ref>

=== Constitutional legality ===
The principle of legality can be affected in different ways by different constitutional models. In the [[United States]], laws may not violate the stated provisions of the [[United States Constitution]] which includes a prohibition on retrospective laws. In the [[United Kingdom]] under the doctrine of [[Parliamentary sovereignty]], the legislature can (in theory) pass such retrospective laws as it sees fit, though article 7 of the European Convention on Human Rights, which has legal force in Britain, forbids conviction for a crime which was not illegal at the time it was committed. Article 7 has already had an effect in a number of cases in the British courts.

In contrast many written constitutions prohibit the creation of [[Ex post facto law|retroactive]] (normally criminal) laws.{{citation needed|date=December 2012}} However the possibility of statutes being struck down creates its own problems. It is clearly more difficult to ascertain what is a valid statute when any number of statutes may have constitutional question marks hanging over them. When a statute is declared unconstitutional, the actions of public authorities and private individuals which were legal under the invalidated statute, are retrospectively tainted with illegality. Such a result could not occur under parliamentary sovereignty (or at least not before ''[[Factortame]]'') as a statute was law and its validity could not be questioned in any court.

=== Principle of legality ===
{{Main|Principle of legality in criminal law}}

The principle that no one be convicted of a crime without a written legal text which clearly describes the crime is widely accepted and codified in modern democratic states as a basic requirement of the rule of law. It is known in Latin as {{lang|la|[[nulla poena sine lege]]}}.