Originally Posted by MAfan
Basically it is a decree issued by the Grand Duke.
Indeed, the British equivalent is an Order in Council, a Proclamation, a Royal Warrant, a Letter in Patent. An Arrêté Grand-Ducal
is the same as a Koninklijk Besluit
(Royal Decree) in the Netherlands (both Countries were under one Crown until 1890). Whatever the exact name, it all means an executive form of legislation based on a higher Act (a parent Act). No parliamentary vote is required, since it is always in the framework of a higher Act.
In an Arrêté Grand-Ducal
always the source (the parent Act) on which it is based, is named.