The Mutual Legal Assistance in Criminal Matters Treaty (“MLAT”) is one way in which incriminating evidence in Canada can be shared with prosecutors in the United States ("U.S.").
In U.S. v. Conrad Black,  O.J. No. 1304, the Ontario Attorney General brought an application under MLAT, pursuant to a request by the U.S. Department of Justice for the gathering and sending of 13 boxes of documents which were the subject of a pending U.S. criminal charge against Black for obstruction of justice. At the same time, Black was facing the threat of contempt proceedings in Ontario for removing the boxes from his Toronto office, allegedly in violation of an Ontario court order.
This case is significant because one of the documents relied on by the U.S. government in support of its request to the Ontario Attorney General was subject to an Ontario sealing order. Since there was no evidence as to how the Department of Justice had obtained the document, there were no consequences for the apparent breach.
In light of Canadian courts' reliance on protective orders to prevent the use of compelled incriminating evidence in the U.S., the treatment of the apparent breach of a protective order in U.S. v. Conrad Black provides little comfort that these orders will effective.