Gosh, at 16, I think that is a bit much. Kids of that age thrive on peer relationships. I'd let him have a night with girlfriend and a night with friends. That interaction is essential for development. I have a 17 year old and a 15 year old. They crave that friend time. Why does your husband have that rule? I think most doctors would say that isn't really in the best interest for kids. It's damaging and your son will grow to resent your husband. Think you can talk him into changing his mind? You can still set boundaries for what he does.
I read that the issue is your relationship with your husband who is unreasonable in this situation and you have handed him full decision making power. As well, you are supporting his irrationality by saying no to your teen on his behalf. Ask your husband why he is so stubborn on this point and really, really listen and inquire to seek understanding. When he says it will "make them better people", ask him how that works, especially when, it seems, they are already awesome people. Inquire as to how he was raised and if that's influencing his approach. Ask him who told him "No" and provided little to no rationale for it. His, and your, behaviour will likely just cause resentment because it's simply not justifiable. 16 young men who show responsibility the way your son does, deserve a wider scope of freedom. They will take it one way or the other and ultimately, your relationship with him should be more important than the occasional night out to hang with friends. I give my teen full decision making power with a few non-negotiable boundaries. No vaping, no smoking, no illegal drugs. Beyond that, at 16, they becoming an adult and my responsibility is to respect that stage of development. I provide the occasional reminder that I will step in when choices infringe upon my boundaries or are not well planned or thought out. As a result, my teen makes great decisions 98% of the time. At some point, we have to consciously shift our parental framework from overprotectiveness or "because I said so" authoritarian, to one that respectfully allows for our kids to become their own people and adults. We have to remember that they still need guidance and firmness on occasion, less and less over time, but the more we respect their choices, the more respect comes back. Good luck to you.
Why is your husband so restrictive, and so bent on finding ways to say "no" to your son? This is the kind of thing that makes kids not come home during college, and then seldom visit in adulthood.