So the ICW was a big part of Secrets of Dumbledore. I think these were the substantive worldbuilding items:

1. The International Confederation of Wizards has a leader. I don't have access to the script but I think the position was referred to several times as the wizarding world's "Great Leader" (a somewhat unfortunate name given North Korea). It's not clear if this Great Leader is the Supreme Mugwump or if that is a separate position within the ICW. More on that below.

2. The Great Leader is elected by popular vote. It's not clear how large the franchise is (again, more on this below).

3. The current Great Leader presides over the election of their successor and has the power to determine issues of procedure.

4. The term in office of a Great Leader is not clear, but it is suggested to be quite long.

5. There appears to be some sort of process by which the candidates for Great Leader are whittled down to a final group of candidates with the most support and a realistic chance of winning.

6. The Great Leader has the power to nullify arrest warrants and overrule the criminal justice systems of national Ministries of Magic.

7. The Great Leader has the power to declare war on the Muggle world on behalf of the entire wizarding world.

8. Candidates for Great Leader are usually the Minister for Magic of a country. Anton Vogel was simultaneously Great Leader and German Minister for Magic. Both of the main candidates to succeed him, Liu Tao and Vicência Santos, were the Chinese and Brazilian Ministers respectively.

9. However, being a Minister for Magic is not a strict requirement to run, given that Grindelwald was permitted to stand in the election.

So, what are your thoughts on all of this? Mine below.

Supreme Mugwump

The most we know about the Supreme Mugwump comes from two scenes in OotP:

This quote does suggest the position of Supreme Mugwump is of some importance, especially given the notability of being the "first" Supreme Mugwump. Lupin describes the role as being a "chairmanship".

However, the Supreme Mugwump is "appointed" rather than elected. Additionally, Albus Dumbledore served as Supreme Mugwump for many years. It does not strike me as consistent with his character that he would stand for election or campaign for political office. That is something he explicitly rejected. And it's clear he was removed from the role via a vote of officials ("Ministry wizards") not a vote of the wider populace.

So I slightly lean towards the position of "ICW Leader" and "Supreme Mugwump" being different. In the same way a corporation has a Chairman of the Board and a Chief Executive Officer, I would suggest the ICW has a Supreme Mugwump (an appointed chairman) and a Leader (an elected executive officer).

Relationship with National Ministries

I think it's fairly clear from SoD that the ICW is top dog in the wizarding community. The Great Leader has power to overrule national Ministries and to declare sweeping policy changes which affect the entire wizarding world. And obviously, the Statute of Secrecy is an ICW instrument and is the most fundamental wizarding law.

However, it is also clear that the national Ministries have a fairly important role within the ICW, given that almost all the candidates are government officials from national Ministries.

All this pushes me even further towards the idea that in canon, wizarding government is essentially a single, global wizarding government, which rules a single, global wizarding community, and that the national Ministries are like regional chapters of that global government.

Franchise and voting

The voting mechanic is somewhat ambiguous.

Throughout SoD, wizards are depicted using a spell to shoot a firework into the air, the symbol of that firework corresponding to their preferred candidate. This spell is used mostly to show support for the candidate in street demonstrations etc.

However, it also appears that this spell is used to vote for the ICW leader. This makes it difficult to identify who is allowed to vote, as it's not possible to distinguish between voters and those merely showing their support.

On the one hand, the franchise may be limited to a group of representatives sent from the member nations of the ICW. During the first vote, the one which Grindelwald wins, we only see the wizards actually in Bhutan using the firework spell to vote, which suggests only those present in Bhutan are allowed to vote.

On the other hand, the franchise may also extend to the entire global wizarding population. In the second vote, the one Santos wins, the people casting these spells included people in remote locations such as the French Ministry for Magic. Are they voting as well, or are they merely showing support? It's not clear.

 

If there is one worldwide wizarding govt, wouldn't there be some common naming convention? Because MACUSA and its President fly in the face of that. Certainly the use of the words Ministry and Auror support your idea, but MACUSA does not. Also, the American custom of strictly separating from muggles is brought up in FB1 as something antithesis to a British wizard, given that in America marrying a muggle was illegal/frowned upon (at least at the time of the first movie).

So perhaps there are wizard communities which break away from the ICW, or claim greater autonomy than others.

 

I really prefer to ignore FB as canon instead of try to make sense of its absurdities.

 

I always thought the ICW was akin to the EU with a bit more teeth.

ICW has several powers that override the individual states (mainly with the SoS), but direct day-to-day powers remain in the individual nation states. Like the UN and EU, a few big nations dominate the rest, while a few push the buttons of the ICW by barely following the rulings.

In Muggle speak, the ICW would be in-between a political union and a very loose confederacy.

 

I'd have to reread GoF, but from what I remember all the logistical discussion of Fudge and Crouch and other Ministry officials setting up the World Cup seemed to involve them working directly with the Ministries of other countries. If the ICW had this level of importance for international affairs I feel like they'd have gotten more mentions at the time.

And I also have the impression that the FB films are meant to be in the same canon as the original movies, which already threw the book continuity into the blender. They might actually wind up impossible to reconcile in the end.

 

The ministries working together directly, with the confederation watching and being informed of the progress for the International Quidditch tournament, is a more representative idea of how the ICW, (and our very own European and early American unions), works, surely?

If it's a loose confederate nation of nations, then it exists solely for the purposes of the stronger states to reap the rewards in terms of resources, manpower, educational standards and everything in between. Furthermore, a loose confederacy implies the weaker states were subjugated by force from the stronger nations to comply with the party line as it were, sort of like international law in all honesty.

In this scenario, I think it more likely that the ICW would be a coalition of people's from the powerful nations making up the body of power and oversight within the ICW, that by proxy of their position allow them to act in punitive ways towards the weaker nations yet that same position almost compels them to leave the ministries of the strong largely alone, unless there is significant backings from the other powerful nations of the bloc. Case in point, Voldemort and Grindlewald.

That all leads me to believe that the powerful nations of the day that created the ICW, whoever the were or are, were smart enough to recognise that while they also had to come together to hide magic, they had to create a mechanism to go to war with muggles if and when it came to it. Hence, the ICWs "Great Leader".

It wouldn't be to much a stretch to imagine that the ICW is in control of it's own standing army, but for some reason I just don't see it. I think JK looked to the recently forming EU of her time, and drew on her knowledge of the League of Nations and the UN to fit the mold of the ICW, rather than the US federal government's structure.

If that's fleshed out, I think it's probable that the ICW takes its direction from the current mood in ministries around the world, rather than issuing directives to said ministries. Anyone that runs around with Great Leader as their title is having smoke blew up their arse lol.

It's pretty likely in this scenario though that power remains fluid and is always swapping hands and nations to keep everyone happy. There would be times that a strong overreaching visible confederacy would exist and times where it's almost invisible while the balance of power between nations shift.

 

From a fanfic perspective, I think it would be interesting to see some sort of 7 year AU which takes as its starting point the concept that the wizarding world is far more internationalist than depicted in canon.

Something like this...

1. There are around 5 million wizards worldwide.

2. There is a single wizarding government which governs all wizards - the International Confederation of Wizards.

3. The ICW has been headquartered in various locations over the years, but the current headquarters are in London.

4. The ICW runs 11 schools of magic, of which Hogwarts is one. Each of these schools takes students from all around the world, and function as the elite education of the wizarding world. Attendance is free, if you can gain entry by passing the stringent tests, or otherwise through legacy admissions.

5. Other magical schools exist (totaling around 300 schools worldwide) but they are private, fee-paying institutions or otherwise operated by charitable foundations, are considered lower in status and quality to the ICW schools, and tend to serve their immediate locality rather than having global attendance.

6. Accordingly, the population of Hogwarts is larger and substantially more diverse than in canon. As it is located in Britain, it does have a certain preponderance of British students reflecting legacy admissions, but these amount to no more than 40% of the student body.

7. The areas in which these 11 schools are located are the main centres of magic in the world, attracting large amounts of magical immigration, with magical populations disproportionate to the global average "wizard to Muggle" ratio. They also have a rather cosmopolitan population as a result of all that immigration.

8. The wizarding electorate is the Confederation, a membership of several thousand wizards from around the world, somewhat like membership of the Communist Party in China. Membership is not based on nationality, and the members do not represent nations or localities. Rather, membership is based by magical ability as determined by passing a series of tests which are set above NEWT level.

9. Membership of the Confederation is therefore dominated by those who attended the 11 schools, plus a few of the more successful non-ICW schools.

10. As the members do not represent localities but merely themselves as magically powerful citizens of the global wizarding community, the main centres of political gravity in the wizarding world are individual powerful wizards, not nation states.

11. The Confederation periodically elects a governing body of 144 wizards from among their number, known as the Council of Mugwumps (or just "the Council"). This body acts as the day to day supervisors of global wizarding government. The chair of this body is the Supreme Mugwump.

12. The ICW does not have a single, unified executive. Rather, the Council oversees separate executive agencies which are responsible for different areas of wizarding government - secrecy, dark magic, etc. Each of these executive agencies has its own Director, appointed by and answerable to the Council, and they are based in different locations around the world.

13. As a rule, the ICW takes a fairly libertarian, small-government approach to rule, focused mostly on secrecy and serious crime/dark magic, and a great many public goods are left to the private sector to provide (such as the policing of petty crime).

14. Voldemort's movement was a global affair and was played out with the ICW as its venue.

15. As wizards form a single global community without borders, when Muggles go to war and Muggle borders change, it has no impact on the borderless wizarding world.

 

Concerning the question of how the firework spell is related to and functions for voting here are my thoughts:

The spell itself does more than just visibly display allegiances. It literally let's people 'cast' their vote on an election as a spell. Like how muggles can mail their ballot or use online services to vote.

Each person who casts the 'voting spell' is magically counted and the results get mentally transmitted to the officials overseeing the election process. This could perhaps give them a general sense of how the scales are tipping as the opinions of the public changes.

Once a wizard has cast their vote for one candidate they may change their vote by recasting the spell at any point before the final countdown has ended or a majority has been reached, I am not entirely sure on that detail. Repeated use of the firework display for the same candidate are likely just meant as a public demonstration; I doubt they would be additive to the actual voting count.

Use of the voting spell is likely restricted to adult wizards, similar to the application of the Trace on those underage. It would also likely draw on the conceptual authority invested in each voter as free citizens of the wizarding community. Sentenced criminals likely lose their right to vote until such a time as their sentence has run its course.

On a purely speculative note there could be some correlation to the Tri-wizard champions' use of glowing sparks during the third challenge of GoF or the Dark Mark cast by Death Eaters. There could be a family of 'signaling spells' used by wizards for a variety of purposes.