What is Judicial Deference?

Legal Definition
Judicial deference is the condition of a court yielding or submitting its judgment to that of another legitimate party, such as the executive in the case of national defense. It is most commonly found in countries, such as the United Kingdom, which lack an entrenched constitution, as the essential purpose of such documents is to limit the power of the legislature.

There are some examples, however, of the occurrence of judicial deference in the United States, such as on immigration case law, wherein the judiciary has (historically) sought to not impede explicit constitutional Congressional authority; see Fiallo v. Bell (1977).

In Regina v. Director of Public Prosecutions Ex Parte Kebeline and Others [1999], Lord Hope explained that courts should "defer, on democratic grounds, to the considered opinion of the elected body as to where the balance is to be struck between the rights of the individual and the needs of society." Nevertheless, the doctrine has been criticised for representing a way in which the courts should act obediently to Parliament in order to uphold the doctrine of Parliamentary Sovereignty.

However, any suggestions that the House of Lords was being unduly servile to Parliament were overturned by the decision in A v Home Secretary [2005]. In the case, a group of detainees who had been imprisoned without charge under s.23 of the Anti-terrorism, Crime and Security Act 2001 on the grounds that they posed a threat to national security, appealed successfully against their detention. The court held that the powers of detention without charge violated Convention rights because of their discriminatory impact (articles 5 and 14 Human Rights Act 1998).
-- Wikipedia