The Decennial Census Improvement Act was passed in 1991 to "address growing concerns about undercount in the census". The Act "instructed the Secretary of Commerce to contract with the National Academy of Sciences (Academy) to study the means by which the government could achieve the most accurate population count possible."
"The Act also permits any person aggrieved by the plan to use statistical sampling in the decennial census to bring a legal action and requires that any action brought under the Act be heard by a three-judge district court. It further provides for review by appeal directly to the Supreme Court of the United States." 
- Doc v. United States House of Representatives, 525 U.S. 316 (U.S. 1999)