1. Rub chicken with pepper. In a bowl, combine orange zest, chili powder, and salt. Rub evenly over chicken. Let stand at room temperature 30 minutes.
2. Preheat grill.
3. For the Chimichurri Sauce, process garlic, bay leaves, chiles, salt, and 1/4 cup vinegar in a blender; process until a paste forms, scraping down sides as needed. Transfer to a bowl, and stir in parsley, oregano, and basil. Whisk in remaining 2 tablespoons vinegar, oil and 2 tablespoons hot water until well-combined. Keep at room temperature until serving. (Sauce can be stored in the refrigerator in an airtight container up to 3 days.)
4. Lightly brush grill rack with oil. Place the chicken, skin side down, on grill, and cook, turning occasionally, for 20 minutes or until well-browned on all sides and the internal temperature reaches 165° when tested with a meat thermometer. Arrange the chicken on a platter, and serve Chimichurri Sauce on the side. Remove skin before eating chicken.