Any person who shall sustain injury by reason of any knowing (including willful) violation of a consumer product safety rule, or any other rule or order issued by the Commission may sue any person who knowingly (including willfully) violated any such rule or order in any district court of the United States in the district in which the defendant resides or is found or has an agent, shall recover damages sustained and may, if the court determines it to be in the interest of justice, recover the costs of suit, including reasonable attorneys’ fees (determined in accordance with section 2060(f) of this title) and reasonable expert witnesses’ fees: Provided, That the matter in controversy exceeds the sum or value of $10,000, exclusive of interest and cost, unless such action is brought against the United States, any agency thereof, or any officer or employee thereof in his official capacity.