And there was no effort on their part to deport more, either. That was a choice made by the Obama Administration, and therefore reflects a policy difference between the two administrations. It didn’t just happen all by itself.
Let me explain some basics about the American system of government, since apparently you live somewhere else. Congress does indeed pass laws, but that’s far from the end of it.
First of all, a lot of the time, Congress deliberately gives the Executive a lot of latitude in how it applies the law: it’s written right into the law.
Second, maybe you hadn’t noticed, but there’s this thing called the Federal Register. It’s where regulations and proposed regs are published. Regulations are needed because the laws, in and of themselves, generally fail of being operational. What the regs for a given set of laws might look like depends a great deal on the nature of the Administration that writes them. A certain amount of latitude inherently exists in laws, even when Congress writes them pretty specifically.
Third, there’s the question of enforcement of laws. The Executive Branch does not have unlimited resources, and many laws are weakly enforced because Congress provides insufficient resources. Recently, the state of Michigan tried to blame EPA for failing to test lead levels in Flint, Michigan. Republican Congresses don’t like the EPA, and have cut its enforcement budget: it can’t do the sort of testing and inspection that the law theoretically requires.
And the immigration laws, I am told by persons more familiar with them, give the President a great deal of latitude in determining the degree and kind of enforcement he will apply. So you see, even when the laws don’t change, Presidents still have room to make choices within the laws, and budgets may constrain the room they have for choices.
This has been a public service message. 