GAO: NASA Constellation Program and Appropriations Restrictions, Part II B-320091, July 23, 2010

"Congressional Requesters: In a letter dated March 12, 2010, you requested information and our views on whether the National Aeronautics and Space Administration (NASA) complied with the Impoundment Control Act of 1974 and with restrictions in the fiscal year 2010 Exploration appropriation when NASA took certain actions pertaining to the Constellation program. ... CONCLUSION: NASA's actions to date with regard to the Constellation program have not violated either the Impoundment Control Act of 1974 or the provision in the fiscal year 2010 Exploration appropriation that bars NASA from terminating or eliminating any PPAs of the architecture for the Constellation program."