Der Begriff ist ein normaler juristischer Begriff. Er wird meistens im Zusammenhang mit der zeitweiligen Suspension von Grundrechten verwendet. Besonders wichtige Grundrechte sind demnach non-derogable. Er ist ursprünglich ein katholischer Begriff.
Catholic Encyclopaedia bietet die beste Definition:http://www.newadvent.org/cathen/04739b.htm
The partial revocation of a law, as opposed to abrogation or the total abolition of a law. This definition of derogation first introduced by the Roman jurisconsult Modestinus (XVI, 102, De verb. significatione) was soon adopted in the canonical legislation.
Law Library: http://www.lectlaw.com/def/d144.htm
DEROGATION - The partial abrogation of a law. To derogate from a law is to enact something which is contrary to it, while to abrogate a law is to abolish it entirely.
v. der·o·gat·ed, der·o·gat·ing, der·o·gates
1. To take away; detract: an error that will derogate from your reputation.
2. To deviate from a standard or expectation; go astray.
aus der Wikipedia:
Derogation is the partial revocation of a law, as opposed to abrogation or the total abolition of a law. The term is used in both civil law and canon law. It is sometimes used, loosely, to mean abrogation, as in the legal maxim: Lex posterior derogat priori, i.e. a subsequent law imports the abolition of a previous one.
Derogation differs from dispensation in that it applies to the law, where dispensations applies to specific people affected by the law.
In terms of European Union legislation, a derogation can also infer that a member state delays the implementation of an element of an EU Regulation (etc) into their legal system over a given timescale, ie, five years.