State Secret Protection Act of 2008

State Secret Protection Act of 2008 - Declares that in any civil action brought in federal or state court the government has a privilege to refuse to give evidence and to prevent any person from giving evidence only if the government shows that public disclosure of the evidence that the government seeks to protect would be reasonably likely to cause significant harm to the national defense or the diplomatic relations of the United States.

Requires the court to take steps, including in camera hearings and other proceedings, to protect sensitive information that comes before it.

Sets forth rules regarding the participation of counsel or the disclosure of information when it presents a risk of harm. Provides for court-ordered presentation of adequate or nonprivileged substitutes for privileged evidence.

Allows the government to: (1) assert the privilege in connection with any claim in a civil action to which it is a party; or (2) intervene in a civil action to which it is not a party in order to do so.

Provides that once the government has asserted the privilege, and before the court makes any determinations, the court shall: (1) undertake a preliminary review of the information in question; and (2) provide the government an opportunity to seek protective measures under this Act.

Establishes procedures and a standard for assessing the privilege claim.

Allows disclosure of an item of evidence to a nongovernmental party, or admission at trial, if the court determines that the privilege is not validly asserted. Prohibits such disclosure or admission if the privilege is determined valid.

Grants the courts of appeal jurisdiction of an appeal by any party from any interlocutory decision or order of a U.S. district court.