In 1954, the Dutch and the Flemish (northern Belgian, Dutch-speaking) collaborated to publish the first Green Book,* the standard of "preferred Dutch" spellings.
This was preferred, specifically, over "allowed Dutch."
The "allowed (toegelaten) Dutch" of 1954 contained a lot of variations in spelling, compared to "preferred (voorkeurspelling) Dutch." These variations were often due to the foreign origin of words. "Preferred Dutch" mostly straightened out the variation, spelling words according to phonology — more-or-less. Official Dutch today is highly phonetic — more so than English, for example; but less than Spanish.
The Green Book itself it not the legal arbiter of proper Dutch, but is based upon the "spellingbesluit." The spellingbesluit is regulation, mandatory for governmental and educational use.
The spellingbesluit of 1996, instituting the nieuwe spelling, was drafted by experts in cooperation with the Dutch-language Union. (Nederlandse Taalunie.)
The Green Book, without official status, is nonetheless the "non-official official" reference.
It is produced by the Nederlandse Taalunie for use in Holland, Flanders, Suriname, and the Dutch Antilles. The governments in these regions determine how to conform to the specification.
The Green Book, of course, is always in modification, through addenda and in reprint. In 1994, the Taalunie determined that the spelling system would be ammended every ten years; this would involve a new printing of the Green Book and a coordinated spellingbesluit. Presumably, changes in spelling rules would be minor, compared with those of the "nieuwe spelling" of 1996 — the most important function probably being the treatment of words acquired in the interim.
The most recent Green Book reprint occured in late 2005; the minor changes in rules that pertain to this incarnation of Dutch became official in The Netherlands as of August 2006.
There has of course been debate and controversy about stipulations made in the spellingbesluit, and suggestion too that government has no place making rules about the language.
But that's Dutch. And as long as the Dutch are involved with it, Nederlands will probably always be a work in progress, and a matter for civic discussion.
