This weird law was established in 1995 at the height of the cold war. The US attempted to weaken Castro's authority in the country by allowing his people safe passage into the US.
This has led to many Cubans crossing the waters in small boats over the past 20 years. Other refugees are not given the same liberties as Cuban refugees making the law favor the Cuban refugees.
"Effective immediately, Cuban nationals who attempt to enter the United States illegally and do not qualify for humanitarian relief will be subject to removal, consistent with U.S. Law and enforcement priorities," Mr. Obama said in a statement. "By taking this step, we are treating Cuban migrants the same way we treat migrants from other countries."
Suffice the president's move being noble in all sense of the word; the timing is a bit off. Many insist that he said it secret and should have given the Cubans prior notice. But this would only cause the Cubans to get on their rafters in their thousands to beat the deadline.
But that said, there are still many on transits who started the journey before the announcement. It will be interesting to see how the government reacts to them.