Is is appropriate for my husband to try to correct his newphews behavior when he is a guest at our house?

This year we hosted New Years Day dinner at our house. My mom, my brother and his wife, my father-in-law, my sis-in-law, my brother-in-law and my newphew were all there along with my two children 16 and 12 and myself. My newphew is 15 years old and is socially and behaviorally challenged. He was diagnosed with ADD or ADHD but has never really been taught how to behave at the table. My husband feels that since it is his house, he makes the rules and try's to discipline the kid. It drives me crazy as I feel that we are not going to fix that kid in the short period of time that he is in our company. We have rules for our own children and I would love it if my newphew was held to the same standards but his parents are in denial about his issues. To me, my husband sounds like a control freak and it makes me uncomfortable. All though I care, does it really matter if the kids wants to drink and entire bottle of soda or slather ketchup all over his food? It is gross and I have to clean up after his mess, but I tend to let it go where my husband has to make a big deal of showing the kid who is in charge. Every time I host at my home and know that my newphew is coming, my husband and I are at adds about how to handle him.