If you are aware of a crime, you have a duty as a citizen to report it. As a public official, Obama has a greater duty in that regard. He shirked his responsibility
I had a cousin who was a drug addict, and therefore a felon.
Did I turn him in?
No, I did not.
You should have. You would have been helping him, your local community and your country
No, not really.
He eventually got caught & put in prison. It helped him not one whit. Nor did it help his community nor his country.
He was a perfectly respectable citizen, working a job & paying his bills. He got bent
in private in his house in the evening.
He hurt no one.
He was a drain on no one's resources.
Then he went to prison, which was bad for him, and also bad for the community because he wasn't working a job & paying taxes any more. In prison, he was living at taxpayer expense.
Aaaaaaaand we've come rather far from the OP, for which I'm sure MachO joins me in apologizing.
Sen. Obama has announced that
1. He was unaware of his Half-aunt on his father's side's immigration status.
2. He will be returning whatever contributions she has made to his campaign.
So, he couldn't have turned her in anyway, since he didn't know she was here illegally.