If you were to bring an artifact from overseas into the US, how would you go about doing so?

My family inherited an ancient Indian sword that dates back to the 16th century. It was handed down from generation to generation for many years. My family would like to preserve a part of our family history rather than losing it. The problem is that the artifact is left back at their home country and would like to bring it here. How would they be able to bring it across US borders legally without it being confiscated by US authorities?