I play in some CyberGamer.com.au leagues, and the rules go as followed.
Game play Options:
Head shots only: Disabled
Allow perks: Disabled
Allow air support: Disabled
3rd personl mode: Disabled
Hardcore mode: Enabled
Kit restrictions:
Primary
Assault Rifles: No Restrictions
Sub Machine Guns: P-90 & UMP-45 Banned
Light Machine Guns: All Banned
Sniper Rifles: Intervention only
Secondary: Handguns only
Equipment: C4 and Claymores Banned
Special Grenade: Stuns Banned
Attachments: Grenade Launcher, Shotgun, Akimbo, Thermal Scope and Heartbeat Sensor Banned.
Riot Shields are banned.
DeathStreaks:
Copycat only
Perks:
Disabled
Maps:
Afghan
Skidrow
Sub base
Quarry
Invasion
Karachi
Favela
Terminal
This, ofcourse, is the 5v5 SnD ruleset. The rules are fair, in my opinion, when playing proper clan matches. But in pub lobbies we can do what we like. Professionals play the game for fun, too.