No damages, interest on damages, costs or attorney’s fees may be recovered under section 4, 4A, or 4C of the Clayton Act (15 U.S.C. 15, 15a, or 15c) in any claim against a person based on any official action directed by a local government, or official or employee thereof acting in an official capacity.

Subsection (a) shall not apply with respect to cases commenced before the effective date of this Act.