A nation that rules over other nations, known as a dominant or conquering nation, is the founder of an empire of nations.
Empire
The United Nations enforce rules through the resolutions of the Security Council.
countries have to operate their nation according to rules and regulations required by the united nations.
The decision of the legislative body for each nation defines its laws, rules and regulations, which are then carried out by the executive branch. This is true of nations with democratic principles, but not true of dictatorships, for instance.
Africa is a continent, not a nation. The different nations in Africa have different voting rules.
Every nation that supports research on the Antarctic continent does so under the guidelines of the Antarctic Treaty. The treaty specifies that all research is shared among all signatory nations -- those that have signed or ratified the treaty. Individual nations establish their own rules for accepting proposals from principal investigators, and they may differ from each other. These rules may address funding, access, qualifications, audits and governmental inspections of the work.
Every nation has its own history, customs, etc. Usually people from nations ruled by dictators has no culture to change rules.
Because each country needs a set of standard rules on dealing with other nations and their governments, otherwise, each interaction would be different and no relationship would be formed with any other nation. And of course, with an ever-increasing global society, these relationships are very important.
The British document, the Magna Carta, established governmental rules that many nations used as a model for their own documents.
A country, state or nation that rules itself, not by some other country. It is free, it is independent.
There are several ethnically homogeneous nations. Many would consider Japan and North Korea to be the most homogeneous due to tightly imposed immigration rules and several other factors including racism and language barriers (not many non-Japanese can easily speak Japanese).
I have analyzed several grammar books about the right form of verb rules. Some of them explained 22 rules when other one demonstrate 30 rules.