Hello,
Modern Illegal issues & UPU.
1a.) According to the Russian authorities all stamps from Russian regions (sub devisions) are illegal issues and have never been valid for postage.
Here is the names and a map of the Russian sub devisions.
Vinculo (http)
Any misspelling or alternative names for the these provinces are also regarded as illegal stamps by the same Russian authorities.
1b.) Example:
Chechen Republic, Chechenskaya Respublika; Chechen Chechnya
Chechnya; Chechen Chechnia or Chechenia, Ichkeria etc
Vinculo (http)
I´ve been in Chechnya twice when it was semi-independend and
they had their own air routes to Turkey , Syria and The Emirates. However, even at that time the post was run by the Russian Post using Russian stamps. So no stamps was ever issued for postage.
As a globetrotter I recommend not to try to buy or sell or even
have in position any illegal stamps in your pocket if you travel to Russia.
Sorry but Illegal issued stamps are not regarded as stamps nor labels in Russia

Probably they are not illegal to posses in most countries
but for sure they are not postage stamps. However, to try to sell them
as legal issued postage stamps anywhere in the world is not recommended.
2.) There´s a big misunderstanding that only stamps from members
of the UNIVERSAL POSTAL UNION (UPU) are legal issued stamps
valid for postage.
Here you have the list of UPU members and others which have their mail
routed via a third country country. As you can see dependencies falls under the "mother member" of UPU.
Vinculo (http)
This list is not complete as for example Alderney falls under Guernsey as
It is a part of the Bailiwick of Guernsey.
Further some corrections are also needed for the countries with limited recognition having their mail routed through third countries.
-Abkhazia mail routed through Russia
Still a little bit tricky to know if it works with officially issued stamps.
A lot of bogus stamps exists.
-Northern Cyprus mail routed through Turkey
Mail is routed and officially stamps are issued and used.
-Kosovo mail routed probably via Albania
Mail is routed and officially stamps are issued and used.
Some bogus stamps exists.
-Somaliland mail is probably routed through Ethiopia.
Mail is routed but no stamps have been officially issued yet
and they do not have any post offices.
A lot of bogus stamps exists.
-South Ossetia mail routed through Russia.
Still a little bit tricky to know if it works with officially issued stamps..
A lot of bogus stamps exists
Nagorno-Karabakh mail routed through Armenia
-Mail is routed and officially stamps are issued and used.
Some bogus stamps exists.
-Palestinian Authority
Well, stamps are listed in the main stamp catalogues and they have a lot of post offices. However, for example, Canada has stop accepting mail to Palenstina as all is returned. Any one been receiving mail from Palestina with palestinian stamps recently?
-Transnistria mail routed by Russia via Ukraina.
Still a little bit tricky to know if it works with officially issued stamps.
A lot of bogus stamps exists.
-Sahrawi Republic mail routed through Algeria but not with
any stamps issued by the Sahrawi Republic. They do not even have a
post office in the territory they control. (marked in red at the map (link)
A lot of bogus stamps exists.
Vinculo (http)
-Taiwan (Republic of China) routed through a third countries.
-Mail is routed and officially stamps are issued and used.
They are even using the EMS post system wich UPU oversees.
without being an member of UPU
Probably there are some more to add but I can´t remember right now
and things will definitely also change.
Then we have course all ex-Russian republics which today
are members of UPU. However a lot of bogus stamps exists.
Every one is not a bad guy and intentionally trying to sell illegal stamps
but with accurate information we can all do better and get it sorted out
in a nice way. Stamps as stamps, labels as labels and no illegal stamps.
Good Luck to The Delcampe Team, The Moderators and all of us.
Regards
El Gringo
P.S. This link....
Vinculo (http)
...shows only stamps from some of the UPU member countries, not all.
Further, it´s even incomplete as some issues are missing from the country lists. Conclusion; the only thing you can be sure about is
that the stamps you can see at the site are legally issued.