The United States changed its copyright law in 1976 so that works are now copyright for approximately the same length of time they are in Canada.
But for the next half-century there will still be books which are copyright in one country but not in the other.
Until the new U.S. law went into effect January 1, 1978, the copyright period (including renewals) was 75 years from the date a work was published. The Canadian copyright period is 50 years from the author's death.
Under the new U.S. law, works published after January 1, 1978, will be copyright until 50 years after the author's death—and the copyright period for all works, old and new, stretches until December 31 of the year in which the time period expires.
The difference in copyright periods in the two countries leads to some complicated cases. The Sherlock Holmes stories of Sir Arthur Conan Doyle provide an example.
The first novel, A Study in Scarlet, was, first published in England in 1886 and in New York in 1888. The U.S. copyright should thus have expired in 1963.
Another novel, The Hound of the Baskervilles, was published in both countries in 1901 and 1902, so that the American copyright expired in 1977.
But The Valley of Fear, published in 1914, stays under the protection of U.S. copyright until December 31, 1989.
In Canada, all books remain protected by copyright until fifty years after the author's death. That anniversary will be July 7, 1980.
As long as the books are copyright in Canada, even if they are "in the public domain" in the United States, it is probably illegal under the copyright act to import U.S. copies of them into Canada without the consent of the copyright owner.
But, as the 1977 working paper on copyright points out, "it is difficult to see how Revenue Canada could properly enforce" that law, given the vast amount of printed matter coming into Canada all the time.