Adding on to Bender's post, most of the blocking I've seen happens at consumer oriented ISPs. Sometimes the regulator only asks mobile carriers, so residential wired internet still works fine. Sometimes they'll get residential and mobile, but not offices. If there's in country servers/datacenters, those might not have filtering and also be reachable domestically.

It really depends a lot on what's going on that they want to block. Making it hard for people to do X is often good enough. For some things, making it unreliable is more effective than a complete block, because a complete block leads people towards circumvention but unreliability can push towards local alternatives instead.