On December 8, 1993, the North American Free Trade Agreement Implementation Act extended copyright protection to certain motion pictures first fixed in Canada or Mexico between January 1, 1978, and March 1, 1989, and published without a copyright notice.

A year later, on December 8, 1994, the Uruguay Round Agreements Act restored copyright to certain foreign works under protection in the source country but in the public domain in the United States.

By White House [Public domain or Public domain], via Wikimedia Commons.

Reposted from the History of Copyright Timeline at the U.S. Copyright Office.