From the FAQ:
"The U.S. states that do not allow skill-based gaming are: Arizona, Arkansas, Connecticut, Delaware, Florida, Iowa, Illinois, Louisiana, Maryland, Montana, South Carolina, South Dakota, Tennessee, and Vermont
The countries that do not allow skill-based gaming are: Brazil, Argentina, the People's Republic of China, South Korea, Japan, and any other jurisdiction that WGT excludes in its sole discretion."
My guess is that if you add your billing info, as per Icon's suggestion, you'll be able to play any tournament you want.