What is the case law on national security and international relations in the context of national security considerations?

For example, Chief Justice Thurlow in Goguen v. Gibson, [1983] 1 F.C. 872, at 881, wrote: In a small claims action its importance might not easily prevail over that of the public interest in national security or international relations. In a criminal prosecution for a capital or other serious offence its importance could weigh very heavily if the information is shown to be of critical importance for the defence or for the prosecution.