Pursuant to a congressional request, GAO provided information on the legality of the Environmental Protection Agency's (EPA) cross-border sales of vehicles certified to meet California clean air standards, focusing on whether EPA: (1) is required to issue a rulemaking policy on cross-border sales; and (2) acted properly in taking action on a matter concerning a rulemaking petition. GAO held that: (1) EPA was not legally required to announce its rulemaking policy, since it did not implement its policy change; and (2) the petition for rulemaking did not limit EPA discretion to take any actions related to the issues covered by the petition.