And that in the US systems are not copyrightable: https://www.law.cornell.edu/uscode/text/17/102

Example 1: If someone views https://www.lego.com/cdn/product-assets/product.bi.core.pdf/6259467.pdf (generic airplane), and physically creates the model with Lego bricks, is there copyright infringement?

Example 2: If someone looks at a picture of LEGO bricks: https://www.flickr.com/photos/shamisenfred/50193102497/ and builds the same result, is there copyright infringement?

If there are no trademarked or registered copyrighted works present in the Lego bricks, is it infringement to then sell that collection of Lego bricks and/or custom generated instructions that use no LEGO brand assets or trademarks with a disclaimer that it is not an official Lego product? (People are doing this, but the part that’s unclear is “is there copyright on the Lego creation itself, or just the “cookbook” that is the instruction manual and graphics therein?)

It is 1000% clear that you cannot reprint LEGO group or anyone else’s instruction book as that would be clear cut copyright infringement. My understanding is that two people could produce instructions that generate the same result as they describe a system for building.

So Lego Group and anyone else who creates their own custom instruction manual can have copyright over the manual as an expression, but not the system it builds is my understanding.

If you are a Lawyer or know a lawyer who'd be interested in talking more, I'm happy to pay for your time. Make sure your email is on your profile or link to it here. HN has all walks of life so there may be one here!