I don't know the details of that particular case, or of the Swiss in general, but the idea sounds really disturbing. I could just as easily translate "the supreme court has now voided the result on the grounds that voters were not given full information, and the vote must be re-run." into:

"The elites decided that the expressed will of the people can be ignored, because they were not exposed to enough propaganda beforehand to convince them to select the choice that the elite wanted. We'll just keep holding new referendums and pumping out propaganda until they make the correct choice, i.e. the choice that the elite want."

Well it was a pre-existing law, so it's not like the govt turned round and effectively said "sorry, wrong answer - try again". Anyway in this case it was the government found to have put out misleading information.

Not perfect, but not a bad sanction against achieving a result via disinformation or outrageous advertising claims.