According to the "Vienna Convention on the Law of Treaties 1969"
Article 32 Supplementary means of interpretation
Recourse may be had to supplementary means of interpretation, including the preparatory work of the treaty and the circumstances of its conclusion, in order to confirm the meaning resulting from the application of article 31, or to determine the meaning when the interpretation according to article 31:
(a) leaves the meaning ambiguous or obscure; or
(b) leads to a result which is manifestly absurd or unreasonable.
Imagine all the arguments, rebuttals, motions for and against ACTA, what do they really mean when we don't know the true intention behind the treaty. All of the preparatory work of the treaty are sealed by the United States Trade Representative's Freedom of Information office, siting national security as the reason they are not available to the public. So any argument for or against cannot be substantiated. We can only guess the true intent of the treaty by what has come before and what is planned post ACTA. Do you want to put your money on a treaty that was penned by the entertainment stake holders, and would you trust a country who trusts the entertainment leaders over their own citizens with their national security?