To counter past assertions that permutation testing is not distribution-free, this article clarifies that the critical p value (alpha) in permutation testing is not a Type I error rate and that a test's validity is independent of the concept of Type I error.
Anderson, Richard B.
"Conceptual Distinction between the Critical p Value and the Type I Error Rate in Permutation Testing,"
Journal of Modern Applied Statistical Methods:
1, Article 2.
Available at: http://digitalcommons.wayne.edu/jmasm/vol12/iss1/2