Use guillemets for outer quotes and quotation marks for inner quotes with csquotes

Question

With csquotes in the Norwegian language, quotes at the inner level will be displayed with single angle brackets, and with guillemets at the outer level.

\documentclass{article}
\usepackage[nynorsk]{babel}
\usepackage{csquotes}
\begin{document}
\enquote{Guillemets at the outer level, but \enquote{single quotation marks} at the inner level}.
\end{document}

This is a very unusual choice, and I'd like to know where the authors of csquotes got this from. I have never seen it in any Norwegian text (although it does apparently exist).

The most common way of displaying inner quotes in Norwegian, and the ones mentioned in style handbooks, is either:

1. Use guillemets.
2. Use singe quotation marks (as in American English).

As indicated in me MWE, I'd like to go with option 2 here. This means I need to make csquotes use guillemets for the outer level, but quotes for the inner level. How can I do that?

Answer 1

You can declare your style using \DeclareQuoteStyle and then select it with \setquotestyle:

\documentclass{article}
\usepackage[nynorsk]{babel}
\usepackage[T1]{fontenc}
\usepackage{csquotes}

\DeclareQuoteStyle{mystyle}
{\guillemotleft}{\guillemotright}
{\textquoteleft}{\textquoteright}
\setquotestyle{mystyle}

\begin{document}
\enquote{Guillemets at the outer level, but \enquote{single quotation marks} at the inner level}.
\end{document}

Answer 2

You can adapt and create new quote styles quite easily using \DeclareQuoteStyle

In your case

\DeclareQuoteStyle[sverre]{norwegian}
  {\guillemotleft}%  opening outer
  {\guillemotright}% closing outer
  %[0.025em]
  {\textquoteleft}%  opening inner
  {\textquoteright}% closing inner

seems appropriate.

I have commented out the middle optional argument, it provides additional kerning if two quotation marks of different quote levels end up adjacent to each other. Choose a value you seem fit.

For a list of available quotation marks see Table 6 on p. 31 of the csquotes manual.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[nynorsk]{babel}
\usepackage{csquotes}

\DeclareQuoteStyle[sverre]{norwegian}
  {\guillemotleft}
  {\guillemotright}
  %[0.025em]
  {\textquoteleft}
  {\textquoteright}

\ExecuteQuoteOptions{norwegian=sverre}

\begin{document}
\enquote{Guillemets at the outer level, but \enquote{single quotation marks} at the inner \enquote{level}}.
\end{document}