system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does Lego not take down knock-off brands like Lepin?
gpt
>Why does Lego not take down knock-off brands like Lepin?

LEGO *can't* take them down, because Lepin isn't doing anything illegal.  LEGO's relevant patents have expired, so making knock-off brands is perfectly legal.  This is exactly how patents are supposed to work:  Give a company time-limited exclusivity for a novel invention that will eventually expire and allow anyone to make the item.  It encourages innovation without locking that innovation away from competitors forever.