Simple, $ When the gas shortages happened in the 70s, a law was pass limiting the prices of US sourced oil sold domestically. It was put in place to lower the

Simple, $ When the gas shortages happened in the 70s, a law was pass limiting the prices of US sourced oil sold domestically. It was put in place to lower the "oil shock". I do not know the status of that law, but I assume it still exists. So, US source oil can be sold at a higher price if exported and that forces the US to import to make up the difference. I think there was a loophole that allowed this to happen, probably it was not thought at the time it would be viable to export US oil or US would never have the oil to export.