Apparently its hard coded into the game. It can probably be patched, but not without breaking core aspects of the game, and the only reason this activates is because the unique meta-data gets changed with a patch / crack. Hell it might take them a month or so to find a workaround, but that's long enough that nobody can enjoy playing the game. My bet is it takes them just long enough to hold off the initial wave of piracy / frustrate pirates enough to force people to buy the game. And i checked, and i havent found a patch for this. Croteam possibly put this in a core file somewhere.

Either way, i hope most newer games take this route of fudgeing spoon up if you pirate it. Especially because this is a better alternative to DRM since it doesn't screw over legitimate customers.