Why is Washington, DC letting states enforce federal laws?

I've been reading a lot about how states are coming up with their own immigration laws and such laws that give local law enforcement officials federal power basically. Don't you think the Obama administration should be more careful about what the states are doing...? Just saying because I personally think that the states should leave those kinds of things with the feds and not put that kind of power into the hands of law enforcement officers in their communities because that's going to cause a lot of problems like people claiming racial discrimination or other things like that. I'm not racist either because I'm white and I'm married to a black woman who works with the government center in our town.