Unresolved: How to enable WiFi channels above 11 on US MacBook Pro

The next (still) unsolved issue for me is how to enable channels 12-13 on my US MacBook Pro (early 2011 model) with Snow Leopard 10.6.8. The problem is because I bought my MacBook in US where the WiFi channels above 11 are banned but now I'm living in Russia where the channels 12 and 13 are allowed and (thanks God not very widely) used. I've googled for several evenings but can't find the solution. Damn it. It's double strange because my US iPad works just fine in Russia so I couldn't imagine the ability of any problems with WiFi on more expensive and mature device like MacBook. I'm still in research.