If a game is region-restricted, it will be mentioned clearly on the box. Only if special regional pricing is involved will you not be able to play it after moving to another country. So, a game activated in the UK should work fine in the US. My Orange Box clearly mentions the region the game is meant for and if I try to run it while in, say, US or Australia, it won't work. In such cases, one can ask Steam Support to remove that game from the account and buy it again from the Steam Store to get an unrestricted license to the game added to their account.
BTW, I hate CS. Maybe it is because I am terrible at it. The only MP game that really had me hooked was World of Warcraft.
BTW, I hate CS. Maybe it is because I am terrible at it. The only MP game that really had me hooked was World of Warcraft.