I don't believe they enforce anything themselves, but i would feel out of place without a button down shirt tucked in, at least. Probably better off with slacks not jeans, but that's debatable.
Ive been in two in a t & hoodie. One in austin & one in richmond. The visit in nashville i was dressed a little nicer but that was because i was visiting with my folks all day.
Agree with the previous posters.
I'd say business casual. No strict policy in place, to my knowledge, but I haven't ever gone wearing anything weekend causal.
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