In general when in doubt, I would pick "Miscellany" as type and not fill out editor or author if I felt there were none of those.
The system is trying to follow the citation types of BibLaTeX (for LaTeX output) and CSL (for all other types of output).
So for cases where it does seem clear, I would look at appendix 3 and 4 of the CSL specification: http://docs.citationstyles.org/en/1.0.1/specification.html#appendix-iii-types
And possibly at the BibLaTeX manual: http://mirrors.ctan.org/macros/latex/contrib/biblatex/doc/biblatex.pdf
If these documents are too technical, you can also try to look at what people using citation managers like Zotero or Mendeley are using, as they are also using CSL for final output.
Notice also that even though some fields are marked as optional and others are obligatory, the system does not prevent you from storing an entry without the obligatory fields filled out.
I am giving you this answer, rather than something more concrete, as I would image there are different views on who should be mentioned as the author or editor of the text you mention. It could for example be argued that the text has an institutional editor or author being "Folketinget" (parlament) or "Dronningen" (The Queen) or some such thing. There can be rather long debates about that, so it's better to see what came out of those debates than tyr something entirely new.