New York Times: Canadian oil exporters fear that a low-carbon fuel standard adopted by California last week threatens to upset a thriving North American trade in petroleum if the regulation spreads throughout the United States. The California Air Resources Board’s (ARB) low-carbon fuel regulation — the first of its kind in the world — seeks to grade transportation fuels by carbon intensity and set a threshold beyond which refiners would be penalized for using carbon-heavy fuels. While it is …