They applied for a trademark and were rejected due to the term being too generic/descriptive. It has nothing to do with whether they hold IP.

That list doesn't appear to be "legally binding" in a general sense; to me, the way you worded that implies "there is a law saying OSD is the definition of open source in this country" which is very far from the case.

Instead that list appears to be specific cases/situations e.g. how some US states evaluate bids from vendors, or how specific government organizations release software. And many things on that list are just casual references to the OSI/OSD but not laws at all.

A trademark is literally a form of IP. Clearly you don't know what you're talking about.

I didn't say a trademark isn't a form of IP. I said their application for a trademark was rejected due to "open source" being too generic/descriptive, not due to the reason you directly asserted above ("They don't hold the IP, I don't really see any way they could be granted a trademark on it").

You can read more about this at https://opensource.org/pressreleases/certified-open-source.p... or https://www.techmonitor.ai/technology/open_source_initiative... among many other sources. Or a much longer blog post from a lawyer who is active on HN: https://writing.kemitchell.com/2020/05/11/Open-Source-Proper...

fwiw, a non-OSI attempt to trademark "open source hardware" was also rejected for the exact same reason. https://opensource.com/law/13/5/os-hardware-trademark-reject...