Make it illegal for the United States to participate in the world oil market. If the Democrat controlled congress makes it illegal for American traders to buy and sell petroleum, America will face massive shortages. The only oil we will receive will be at the mercy of dictators like Venezuela's Hugo Chavez. With the U.S. removed from competive bidding process, world petroleum prices would indeed drop.
It would also force American industry to relocate to countries that still trade on the world market, leaving America without oil and without industry. This would make Marxists like Kofi Annan very happy.