In the US and EU, even a blocked number can reach 911 or 112. But more relevantly, can bypass blocks. If you call from a landline or a different carrier, sometimes the "block list" doesn't sync perfectly. But this is a glitch, not a feature.
However, there is one network layer untouched by blocks: how to unblock a phone call
But what if you need to get through? What if it’s an emergency? What if it’s a client who accidentally fat-fingered the block button? Or what if you’re just stubborn? In the US and EU, even a blocked number can reach 911 or 112