Four in ten people live in one
Roughly 40 percent of the world's population lives in countries described as federal. That is a lot of people living under two layers of government at once.
In a federation, power is split between a central government and a set of regions, such as states or provinces. Each region keeps some control over its own internal affairs. The key detail is that this split is written into the constitution. Neither side can change it alone. They have to go through the formal process for amending the constitution.
Germany, with its 16 states, and Nigeria, with 36 states plus a federal capital territory, are both federations. France and Japan are not. They are each a unitary state. Federations are often big and home to many ethnic groups, like Russia, the United States, Canada, India, Brazil and Australia. But tiny Saint Kitts and Nevis and the Federated States of Micronesia are federations too.
From 1789 to 2015
The United States is the oldest federation still standing. Its constitution took effect on 4 March 1789. The newest is Nepal, whose constitution went into effect on 20 September 2015.
The idea is much older than either. Groups like the League of Corinth, from the 4th century BCE, and Noricum in Central Europe could be described as federations or confederations. Not every attempt lasted. The Federal Republic of Central America split into separate countries less than 20 years after it was founded.
Countries also got there in very different ways. Australia is unique because it became a nation through a democratic vote in each state, where citizens said yes in referendums to adopt its constitution. Brazil became a federation only after its monarchy fell. Some Brazilian states still keep borders drawn during Portuguese colonization, before Brazil even existed, while its newest state, Tocantins, was created by the 1988 Constitution.
Who handles what
So who does what? The federal level usually handles defence, foreign affairs, money and trade between regions or with other countries, though the exact list changes from one federation to the next. Many federations also give the regions a voice through an upper chamber of parliament.
The regions usually have no say in foreign policy, so they have no independent standing under international law. German states are an exception. They do have that power, and they are starting to use it at a European level.
Not every region has to get the same deal. In asymmetric federalism, some regions have more freedom than others. Malaysia is an example. Sarawak and Sabah agreed to join the federation on different terms from the states of Peninsular Malaysia. When the two levels of government disagree over who controls what, federal constitutions usually name a court to settle the argument.
When the name says the opposite
Names in this field can be misleading. Switzerland is still officially called the Swiss Confederation, but it has been a federal state since 1848.
A confederation is something looser: a lasting union of independent countries that act together toward the rest of the world. Its shared institutions answer to the member states, not the other way round. Canada used the word confederation when its federal system was set up in 1867, but Canadians use it for the act of forming or joining the country, not for its structure. Canadian provinces are not independent and do not claim to be.
The European Union is the closest thing to a confederation today, yet experts still argue about what it really is. In 2009, Germany's Federal Constitutional Court described it with the German word Staatenverbund, which the court translated as an association of sovereign states. Belgium went the other way. It changed from a unitary state into a federal one through reforms that began in 1970.
Kings, dukes and forest police
Some countries are federations in everything but name. The United Kingdom uses devolution, which means the central government can change the powers of its regions without changing the constitution. Spain gives its autonomous communities more self-government than the regions of most federations get. Some call it federation without federalism.
The Crown Dependencies are an odd case. The Isle of Man and the islands of Guernsey and Jersey run their own internal affairs, while the United Kingdom handles their defence and foreign relations. On the Isle of Man, the British monarch is known as Lord of Mann. In Guernsey and Jersey, the monarch rules as the Duke of Normandy.
Italy is officially unitary, but five of its twenty regions have a special status, and they even kept their own forest police. In Wallis and Futuna, three districts match old traditional kingdoms, and each district council is chaired by its customary king.
