It looks like we will have to treat the extra-biblical books as secondary after all. Here is a disturbing verse I came across in Yobelim/Jubilees 2: 31 :

And the Creator of all matters barak it, but He did not qadosh all peoples and nations to guard the Shabbath on it, but Yisra'el alone - they alone He permitted to eat and drink and to guard the Shabbath thereon on the earth.