The U.S. Census Bureau has the dual aims of releasing useful data while protecting respondent confidentiality. We researched a system for custom tabulation queries of confidential microdata from the American Community Survey (ACS). The data in the system would be protected primarily by suppressing sparse tables. Research showed that the proposed rules would require an unacceptable number of table suppressions, while still being vulnerable to attacks on individual records. We concluded that our system as planned could not be useful while protecting the data adequately. Thus, we are considering other options to fulfill our aims.