Who makes these standards? How are they enforced?
Well, the basics are encoded in the various international agreements that most countries are party to, such as the UN Charter. Beyond that, it's politics. You will find that most governments have a lot of opinions about what is going on in other countries, which they put into practice by whatever means they have and in whatever way seems appropriate - ranging from taking the matter up in bilateral meeting through UN resolutions, political or economic sanctions and in extreme cases, war. Most governments, for instance, do not accept the treatment that Myanmar hands out to its opposition, which puts that on the agenda for most governmental contact and doubtlessly has other effects as well. Nobody says "well, it's their own business what the burmese do, and we're just going to ignore it". Fairly obvious all this, isn't it?