73 Fed. Reg. 67711 (November 17, 2008)
Effective November 17, 2008, 8 C.F.R. 217.2(a) is amended to add Czech Republic, Estonia, Hungary, Latvia, Lithuania, the Republic of Korea, and the Slovak Republic to the list of Visa Waiver Program countries.
The USCIS final rule adding these countries also states that each of the new countries has "agreed that its citizens must obtain an approved travel authorization from U.S. Customs and Border Protection (CBP) via the Electronic System for Travel Authorization [ESTA] and must possess a valid electronic passport." ESTA is not mandatory for the other VWP countries until January 12, 2009.