The four-decade ban on domestic crude exports was originally codified because the U.S. wanted greater energy security during the 1973 Arab oil embargo. The ban was unquestioned until recently, when lawmakers started to consider the unthinkable: that the U.S. may repeal the export ban on crude oil. 

The U.S. is considering repealing the ban because the original reason, energy dependence on unfriendly or unstable foreign oil, is no longer a big worry.

Because of the shale revolution, the U.S. is on track to overcome Saudi Arabia and Russia as the world's largest producer of oil and gas combined.  

According to economist Ed Yardeni, the U.S. petroleum deficit may even go to zero in the next couple of years. Because of America's newfound energy resources, Energy Secretary Ernest Moniz recently suggested that the Obama administration may reconsider the four-decade ban. 

While the Energy Department does not have the authority to relax restrictions, Mr. Moniz's comments is likely a trial balloon and a sign of possible change in policy.

The winners
Large oil companies such as ExxonMobil (XOM -2.01%)ConocoPhillips (COP -1.84%), and Continental Resources (CLR) see no reason for the ban and would win if the law were repealed.

Those companies argue that most U.S. refineries can't easily refine the high-quality crude currently produced in the Bakken and other shale plays. When they were built decades ago, those refineries were designed for lower-quality crude from Venezuela, Mexico, and the Middle East.

The solution, according to the oil companies, is for the U.S. to allow companies to export crude oil to other nations that can handle the higher quality. By allowing for export, the price of Brent crude, which plays a large part in setting the price at the gas pump, may go lower, and American consumers would save money on gasoline.

Not coincidentally, the producers would realize more profits because they would realize a higher price for their crude oil.

The losers
If the ban were repealed, it would be bad news for pure-play refiners such as Marathon Petroleum (MPC -0.32%) and Valero Energy (VLO -0.24%). Crude oil refiners benefit from a wider WTI-Brent spread. Any narrowing of the spread would narrow their profit margins. They would also see lower revenues because they would be refining less crude oil. 

The bottom line
It is unclear whether repealing the law would actually change the price of Brent or gas at the pump in the near term. The Brent oil market dwarfs any amount that the U.S. can export in the near future.

I think the companies opposed to the repeal do so because they are concerned that this may be the beginning of a disturbing trend. They may not see any impact on the bottom lines now, but they will be affected down the road as U.S. exports grow.