I have asked this as well and so have several others. This is the best I can come up with...
Eligibility Requirements: Tournaments are open to individual Organizers and Entrants who are 18 years of age or older or the age of majority in the entrant's state or province/territory of residence, whichever is greater. WGT at its sole discretion may limit the number of Entrants who may enter a Tournament. To set up a Tournament as an Organizer or to participate in a Tournament as an Entrant, you must be a resident of (a) the United States but excluding residents of: Arizona, Arkansas, Connecticut, Delaware, Florida, Iowa, Illinois, Louisiana, Maryland, Montana, South Carolina, South Dakota, Tennessee, or Vermont, or be subject to the laws of one of those states (b) any other jurisdiction that WGT excludes in its sole discretion. Residents of Brazil, Argentina, the People's Republic of China, South Korea, and Japan are also excluded and cannot be an Organizer or an Entrant. Employees, officers, and directors of WGT and its affiliated entities, parent, subsidiaries, advertising, promotional agencies, legal advisors, their immediate family members and persons living in their same household, are not eligible to be an Organizer or enter participate as an Entrant in Tournament. Void where restricted, taxed or prohibited by law.
My guess is that more states have been added to the list above...