Region-locking, the act of making games non-functional if used outside particular parts of the world, is not an uncommon thing in games. It is, however, a big deal for Steam—especially the PC gaming service's trading/gifting market. With widespread region locks now in place, change seems inevitable.

Recently Steam users and developers began to discover that gifting in Russian and Commonwealth of Independent States (CIS) regions no longer worked outside of particular regions. Soon it became evident that Southeast Asia, South America, and Turkey were also affected. The short version? No more trading between those areas and Western territories like the United States. The long version, as uncovered by intrepid souls on Reddit, is quite comprehensive:

RU Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Armenia, Azerbaijan, Belarus, Georgia, Kyrgyzstan, Kazakhstan, Republic of Moldova, Russian Federation, Tajikistan, Turkmenistan, Ukraine and Uzbekistan.

Malaysia Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Indonesia, Malaysia, Philippines, Singapore and Thailand.

Thai Baht Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Indonesia, Malaysia, Philippines, Singapore and Thailand.

Indonesian Rupiah Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Indonesia, Malaysia, Philippines, Singapore and Thailand.

Philippine Peso Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Indonesia, Malaysia, Philippines, Singapore and Thailand.

CIS - U.S. Dollar Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Armenia, Azerbaijan, Belarus, Georgia, Kyrgyzstan, Kazakhstan, Republic of Moldova, Russian Federation, Tajikistan, Turkmenistan, Ukraine and Uzbekistan.

Turkish Lira Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Turkey.

Brazilian Real Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Argentina, Bolivia, Brazil, Bahamas, Belize, Chile, Colombia, Costa Rica, Ecuador, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Peru, Paraguay, Suriname, El Salvador, Uruguay and Venezuela.

Mexican Peso Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Argentina, Bolivia, Brazil, Bahamas, Belize, Chile, Colombia, Costa Rica, Ecuador, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Peru, Paraguay, Suriname, El Salvador, Uruguay and Venezuela.

Singapore Dollar Notice: Gift purchases for Crusader Kings II can only be added to the gift recipient's library if they are in Indonesia, Malaysia, Philippines, Singapore and Thailand.

Japanese Yen No restriction note

Norwegian Krone No restriction note

Canadian Dollar No restriction note

U.S. Dollar No restriction note

British Pound No restriction note

Euros (Tier 1) No restriction note

Euros (Tier 2) No restriction note

These restrictions appear to apply to all games, regardless of specific locks (or a lack thereof) publishers might've had in place.

Based on the fact that places like the US and Britain remain unrestricted, it seems like Valve is doing this to curb unsanctioned trades between places where currency is weak and others where it's relatively strong. As Engadget points out, a Russian Steam game could theoretically cost an American user only a few bucks versus the normal price of $30 or $40 or $60.

Steam has always provided localized pricing, so full price in the US and full price in other regions are very different things. This made exchanges between regions extremely appealing for many, as evidenced by boards like Steam Game Swap and sites like Steam Trading and Steam Exchange.

Valve has never been against trading, but it looks like this aspect—the proverbial back alleys and sketchy parking garages of the practice—was irking them. I've reached out to Valve for official comment, but they've yet to reply. I'll update this post when/if they do.