General rules for tight connections in international flights

I was recently looking for a ticket and one of the cheapest options included a stop-over for only 30 minutes at a major international airport. I estimated it would be impossible to catch the connecting flight and bought a different ticket. Later I wondered: what would happen if I bought a ticket with such a tight connection that it would make it almost impossible to catch the connection? Would the airline be responsible to get you on the next flight? Would you receive compensation? Who would determine whether you should have made it in time but you didn’t? Is there a general international legislation or is it left to the policy of each different airline?