HOI4 Rules:

Banned Countries:
Poland, Czechoslovakia, Yugoslavia, Finland, Sweden, Denmark, Estonia, Austria, Greece, The Baltics, Portugal, Luxembourg, Belgium, Netherlands, Albania, Iran, Sinkiang,  Denmark, Dutch East Indies, Middle East, Ethiopia, British Malaya, Liberia, Chinese Minors, all Latin American countries other than Mexico, Brazil.
Neutral Countries: Countries that cannot be player, attacked, or invited into a faction
Turkey, Saudi Arabia, Iraq, Yemen, Oman, Bhutan,Tibet, Switzerland.

General rules:
#1. No exploits (e.g requesting land without permission, do not engage)
#2. No releasing puppets / releasing nations / releasing yourself to another nation
#3. No starting coups
#4. No boosting ideology unless requested by the player
#5. No spiking tension

Volunteers:
Only infantry divisions.
No lend lease/volunteers to Ethopia.
Cannot naval invade with volunteers

Army rules:
No researching 1943 tanks until 1941.
No space marines (infantry with tanks)
No deleting divisions or changing templates on divisions encircled or about to be encircled or caught by navy.

Airforce rules:
No researching 1944 planes until 1944.
Air Production continous focus is banned.
Only Japan can kamikaze.

Navy:
Cannot set 'Do not engage'
No overstacking carriers
No researching 1945 ships until 1943.
4 carrier per battle/fleet

Nukes:
Cannot research nuclear bombs until 1943

Economy:
No deleting factories
No total mobilization until Barbarossa (except Japan)

Diplomacy:
Majors and commonwealth must stay in historical faction and historical ideology.
AI South American countries cannot join faction.
Minors cannot guarantee.
Yugoslavia or Greece cannot be guaranteed prior to WW2.
Portugal cannot be guaranteed or let into the Allies
Cannot give or get military access from China or Japan

Warring:
No declaring war before 1939 or until WW2 starts, whichever is first.
Max lvl 5 coastal forts and max lvl 5 land forts (These can be surpassed through focuses)
Can justify on 1939.1.1


Country specific rules:
USA:
Can join war after 1940 Oct 1st OR a port in England is invaded
Cannot do black Chamber operation
Cannot invade Venezuela
Cannot attack Japan until Japan has attempted to expand out of Chinese territories OR has joined the war against the allies. (excluding indochina)

UK:
Must guarantee Poland and let them into the allies.
No denying Rhineland.
No defending Czechoslovakia

France:
No denying Rhineland.
No defending Czechoslovakia
If France falls you have to play as Free France
Cannot abandon France until Paris has fallen
Cannot build ports in Europe with the intention of making D-Day easier, and cannot build lvl 1 forts all over the place.
Has to accept Indo-China demand

Germany:
Cannot take focus “Oppose Hitler”
 Cannot take Focus “Form the Reichskommissariat”
Must do Molotov-Rib before the invasion of Poland
Must do danzig or war by the end of 1939 (The focus “Danzig or War” must be taken before starting WW2)
 No Vichy France
Must declare war on USSR between April and December 1941 and not before.
The focus “Atlantic Wall” is banned.


USSR:
Must accept Molotov-Rib and tank treaty
Cannot civil war
Cannot declare on Germany until September 1941
 Can Declare War on Japan only after Jan. 1st 1944 OR Axis has been defeated


Japan:
Must declare war on all members of the United Front at the same time
Must declare war on China by 1938 Jan 1st
 Japan cannot join the Axis
Cannot Declare War on Soviet Union.
Can only kamikaze in these aerial regions: Sea of Japan, Coast of Japan, Yellow Sea, East China Sea, and the South China Sea and can only do it from Japanese airports


Italy:
 Cannot skip Ethiopian War logistics
Must join WW2 3 months after the fall of France
Cannot have Axis units in North Africa before joining WW2.

Spain:
Cannot join Axis or the war. Can send volunteers.

Romania:
Must join Axis and accept Soviet demand for Bessarbia.

Commonwealth:
Must stay Allies