Editing Legality (section)

=== 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.