Relax, GW probably won't or can't sue Sega, this was 24 years ago....
I was randomly browsing the web and I came across a really old game cover and it had Space Marines on it. I thought, Shock horror, is there a 40k computer game I didn't know about. Turns out no, an artist just copied the GW models. Almost exactly the original rogue trader marines. Even the terrible proportions and poses. Not even a hint of trying to make it original.
Its an old game for the Sega Master System and Sega Genesis that came out it 1989. I can't find any marines in screenshots from the game so it looks like it was just the cover artist being lazy and copying.
Look at the dudes in the bottom right.
Do those dudes look anything like this?