Can a federal grand jury be lawfully used solely for purposes unrelated to any criminal investigation?

The Philadelphia chapter of the Council on American-Islamic Relations (CAIR-Philadelphia) wants to know the answer to that question. To get that answer, CAIR-Philadelphia (which I serve as legal director) has already engaged in significant litigation on this issue at the district court level, and we have filed an appeal with the U.S. Court of Appeals for the Third Circuit.