I went to a range to let my dad shoot my suppressed 9mm. While he was shooting a range officer came over to our lane asked to stop the shooting. He then proceeded to ask if I had the ATF paper work to prove it was mine. I then told him I didn't know I was legally obligated to show you anything. He said something along the lines "we're an FFL and are required to ask for ATF paperwork". Is there such a law?