OTTAWA — Environmental concerns over Canada’s oil sands have driven a debate over the process that has lasted for years. Now, some in Canada are trying to change the conversation.

Advocates of oil sand production are arguing that the human rights record of Saudi Arabia and other Middle Eastern oil exporters makes oil sands a more ethical energy source, particularly for the United States.

How successful they will be with Americans remains to be seen. But their argument has clearly caught the attention of the government of Saudi Arabia. Canada’s largest private broadcaster, CTV, has refused to show a television commercial produced by the Ethical Oil Institute, an oil sands advocacy group, after receiving a threat of legal action from a lawyer representing the Saudis. Lawyers for the Saudis have contacted other broadcasters as well in an effort to block the 30-second advertisement.

So far, the main result of the Saudis’ effort has been unexpected publicity for the ad, which had previously been seen only by a relatively small cable television audience, and as a minor diplomatic dispute.