I have found out that there are many so called LEGO compatible bricks. But are those bricks legal in the sense that they are not copy cat of original LEGO.
If there are such bricks - what are they ?
All LEGO compatible bricks are legal. At this point LEGO no longer has a patent on the key features of the LEGO system regarding shape, measurements and connectivity.
This doesn’t hold true for minifigures, those are still trademarked.
Where things get ugly is with the design of sets, and the overall look and feel of LEGO packaging and the LEGO logo. Not to mention the licensing of outside IP such as Star Wars, Harry Potter, Marvel etc. This is why clone companies such as Mega Construx, Kreo and Cobi who make their own designs and work out their own IP licensing deals when needed are considered “legal”, where other companies such as the majority of the Chinese clones who gave us gems like “Star Wnrs” are not considered legal.