How far is too far away when stopping at a red light or stop sign?

Y’know that white line at many lights/signs which indicates the demarcation between you and the intersection? Well, you’re supposed to stop at it… but how far away can you be ? Must you stop on it? How about one foot back? Or one metre back? Three? Ten?

And yes, I’m sure it’s locality-specific… that’s fine. What’s the law where you’re at, if any?