The FTC has published rules on this subject. Go to the link below. You can read the actual text in PDF format by clicking on the blue link on the side of the page that says
"Text Of The Federal Register Notice".
http://www.ftc.gov/opa/2009/10/endortest.shtm
Also check out the link below where the law is explained so a human can understand it!
http://internet-law.lawyers.com/Trut...ure-Rules.html