Surprised to see that filming/photography was banned in Panama Canal

When they were transiting the Panama Canal in the "Zaca" Errol Flynn made a point of mentioning that they weren't allowed to do any filming, due to security reasons or some such. At first I thought this was some sort of WWII-related security measure, but then I realized that this was filmed in 1952 - a good seven years after the end of the Second World War. So maybe this was a Cold War reality?