I'm planning on running a small campaign on an Imperial world. And with all the different worlds out there in the Imperium, you get the feeling that everything is allowed, and everything can exists somewhere (if it remote enough).

My question is what sort of societies that would be in violation of the 40K lore. Basically what sort of things can I not have on an Imperial world.

Example:

Could there exist an Imperial planet that was like earth today? No Ad.Mech, No God-Emperor, democracies, capitalism, welfare-states, different countries, science, etc? (Personally I'd say 'no' to that).

Any technologies that we have today that wouldn't resonate well in the 40k world?

Any social structures that wouldn't work?

Basically, what are the minimum requirements of an Imperial World to "fit" in with the 40k lore?

Could there exist an Imperial planet that was like earth today? No Ad.Mech, No God-Emperor, democracies, capitalism, welfare-states, different countries, science, etc? (Personally I'd say 'no' to that).

Such a world could exist outside the Imperium, but it would not be an Imperial planet. I say that primarily because of "no Ad.Mech, no God-Emperor." Without the basic institutions of the Imperium, like the Mechanicus, the Ecclesiarchy and the Adeptus Terra you don't have an Imperial world.

Any technologies that we have today that wouldn't resonate well in the 40k world?

For me, it's not the technology but the attitude. The Imperium has all the technology that we do, but it's wrapped up in the technomysticism of the Mechanicus and a lot of it is dedicated to the state. For example, I can see a moderately advanced Imperial world having something like the World Wide Web... but it wouldn't be full of chatrooms, TV fan sites and adult entertainment. It would be full of documents for the State, the Church and the Mechanicus. It might even be restricted to only people who are required to use it for their jobs. If it has a public "entertainment" function, that would be pretty much State/Church propoganda.

Any social structures that wouldn't work?

To my mind, the Imperium is biased toward facism but in reality there is nothing preventing an Imperial world from having representative democracies, capitalism, even civil and basic human rights. Such a world would be "odd" and probably viewed with distrust by the Adeptus... simply because a free society leaves the door wide open for rebellion, instability and xenos/chaos influence.

Basically, what are the minimum requirements of an Imperial World to "fit" in with the 40k lore?

As I said above, IMO a world needs to have representatives of the basic insitutions of the Imperium... the Imperial Cult, the Cult Mechancius and (though to a much lesser degree) the Adeptus Terra. A tendency toward facist dictatorships, cyclopean gothic architecture, superstition, violence and insanity are all appropriate but not necessarilty essential.

IMO

Since all Imperial citizens are required to worship the Emperor, and follow the Lex Imperialis (the laws of the Imperium), as well as defer to the Adeptus Mechanicus in regard to matters of technology, no, you couldn't have an Imperial Planet exactly like current day Earth.

A current day Earth in which everyone is either Christian, Islamic or Jewish (or another monotheistic religion) where the God-Emperor replaces God/Allah/Jehovah, where the Adeptus Mechanicus dictates what technology we are allowed to use or not, that has one Imperial Governor to represent the planet to the Imperium at large, and that pays a tithe to the Imperium, could exist in 40k. You can have separate countries and all that, that's not a problem.

The main requirement to be an Imperial Planet is that you worship the Emperor as God, that you have a singular Imperial Governor to represent the planet, that you pay your tithes, and that you follow Imperial/Adeptus Mechanicus law. If you fulfil those, you are fine. Otherwise you are a rebel planet that is in need of being brought to compliance.

Is that requirement about a singular Governor really a must? I.e. are not oligarchical groups/triumvirates/etc. possible? For the purposes of Administratum, there would be one Governor to interface with the authorities, but could not the decision process be pluralistic in the way mentioned?

Von Todkopf said:

Typically there is one planetary governor in charge of a world's government and defense forces. That being said, such does not prevent there being different "nation" states on a planet. There have been a couple examples in the past, but they seem pretty rare amongst the "Imperial" worlds. A lot of hive worlds seem to work along these lines, however. One governor, and then each hive has it's own ruler or council who answers to and/or advises the planetary governor.

-=Brother Praetus=-

I prefer to think of the Imperial Planetary Governor like the old Persian Satraps. Basically, their job is to make sure the tithes or tributes are paid to the Imperium and to enforce the basics of Imperial law. Otherwise the planet is able to continue to do things as it sees fit...

Obviously in the Imperium this goes a little further and religion is enforced and law to a greater degree, which is why more rebellions are common in the Imperium than in the Ancient Persian Satrapies...

In short, I would list the no-go as following

No God beside the God-Emporer
This is obivous

No Tech but what the Mechanicus sanctifies
Criminals might get ways with stuff, but whole government won´t

No skimming of the Tithe
As far as I understood from Tattered Fates, only Colonies are spared from Tithe since they are "under development".

No jibbing about final responsibilties: One planet, one head in the sling
As seen in "Damned Cities", an oligarchy is possible. But still they have one "head figure". The one that will be punished/exchanged if things do not
work out. Of course, this position needs to have SOME final word. Otherwise, only fools would occupy it.

No fraternizing with enemy
It is said in "Into the Storm" (RT) that frontier worlds do have non-hostile contact with aliens. I say, as soon if a part of the imperium would pay closer attention to it (or the planet would start bragging about it), the Governeour would be toast. Perhaps the colony as well.

Von Todkopf said:

As far as the Administratum is concerned, there is one Governor. Who that is, how they are chosen and what actual power they weild locally is entirely dependent on the planet in question... and as long as the tithe get's paid, the Imperium couldn't care less.

Well, it depends partly on whether the Administratum sees the amount of tithe produced as fitting for such a world. If they calculate a bigger output could be generated regarding the level of technology, the size of the population and the resourcefulness of the planet, they would enforce this one way or the other. Presupposing the planet is able to fulfil a tithe grade found fitting by the Administratum, it still has to endure the following:

A couple of ecclesiarchial Missionaries from the Missionarium Galactica, who will take care that he present religions are either brought into line worshipping the Emperor (instead of their respective gods – even though certain prophets and even gods can be included as saints or alter egos of the Emperor) or are eradicated. So “no God-Emperor” would not work under normal circumstances.

A planet the size of modern earth would certainly have a few fortified precinct courthouses of the Adeptus Arbites to reassure the Lex Imperiales is taken care of and help that any potential psykers are collected by the League of Blackships from time to time.

Involvement of the Adeptus Mechanicus depends on whether any technology is seen as worthy of their attention (e.g. STC potential) or tech-heresy (e.g. artificial intelligence). They would take care of both for sure. Otherwise they could even ignore a planet if it’s not worthwhile in their view.

To conclude:
“No Ad.Mech” could more or less work, but problematic for anything better evolved than a Feral World.
“No God-Emperor” normally could not work, even though there are certain Pleasure Worlds and domains of Rogue Trader that lack any real ecclesiarchial presence. But then, these planets cannot really be designated as being part of the Imperium as such then.
“Democracies, capitalism, welfare-states, different countries, science, etc?” could work if the aforementioned facts can be integrated somehow. In my campaign for example I outlined a planet (Zumthor) with a rather small population (still considered Frontier World) and sort of republican government.

Type: Sub-Hive
Size Diameter: 200 km; 70 km (habitat dome)
Government: Republican
Planetary Governor: Chancellor Georg Tyrell
Administratum Representative: Adept-Inerlocutor Dahid Benkad
Adeptus Arbites: Justicar Eric Kai
Population: 50 million
Main Corporation: Zelton Cartel
Affiliation: Fenksworld (Josian Reach sub-sector)

It has a so called Local Colonial Council, which basically is a semi-democratically elected council, with some corporate interests and Adeptus Terra interests represented. It is essentially the Lower House of the government. Here bills are created, debated and presented to the Colonial Executive Board. The Local Colonial Council is comprised of 1,350 so called councillors. The political groups present these councillors for election to the citizens who take a vote to accept the candidate or not.
The current dominant power group are the Centralists. The leader of the group, and essentially the Planetary Governor, is a smooth Scintillan noble by the name of Georg Tyrell. He is an aging war veteran, who has held a staunch arch-conservative position throughout his tenure. However, with recent scandals, allegations of corruption, his popularity has begun to diminish. The Regionalists are expected to make huge gains in the next elections, the leader of the party, Councillor Aaron Bisco, is gaining in popularity and expects to make some serious gains in the elections.
The so called Colonial Executive Board is the upper house of the local government system and ostensibly provides the checks and balances on any new budgetary increases, new local legislation and insure that the Local Colonial Council is conforming to Imperial doctrines. The Chair of the board of 150 is Dahid Benkad, the Chair of the Local Colonial Council also has a seat and the others are made up of those elected by the parties themselves. This system has come under heavy criticism, but no moves to present an alternative form of government have been put forward by anyone within the Administratum.

Most technologies are possible in the Imperium with a few exception. For example the Imperium has no non-warp faster than light travel (only the Necron have that IIRC). Some other things exist but should be kept to a minimum, things such as teleportation-systems are extremely rare artifacts from the dark age of technology, and it would be strange to find an Imperial World where they are common.

Other than that its pretty easy to convert any given technological concept to the Imperium, just make it bulky. The Imperium in general does not use lithe grav-tanks for combat, they use metal boxes with guns. They don't use solar sails to navigate space, they use huge pasma-engines with brute force thrust. Military units don't communicate with earpieces, they carry heavy radio-equipment. The less bulky a solution is the more unusual it becomes, nobles might have grav-engine vehicles and micro-voxes, but never the common man.