Question:

My Father Entered U.S. illegally, Can I sponsor his immigration application inside the United States?

Answer:

If your father entered the U.S. without inspection - illegally without passport or visa, as a general rule, he will have to return to the his native country and have the interview at the U.S. Embassy or Consulate there, after you file the Form I-130 application for him.

There is a problem with having a consular process for persons who have remained in the US in unlawful status for more than 180 days, and they leave before the U.S. permanent residence case is approved, these people will be banned to return to the U.S. for 3 years. If the person remained unlawfully in the US for a whole year or more, then he will be banned of returning to the U.S. for 10 years. If he can avoid leaving the U.S. in the first place, he cannot be banned from returning.