I am not in the legal department. Since I started here, our GC (who is in the legal department -- so not my boss or anything, but someone I will be working with sometimes) has said "we [she and a regulatory lawyer in her group] really need to take you out to lunch sometime." That will happen today.
I should assume she is expensing this and I don't need to make a gesture to pay, right?
If its someone senior to me I do not attempt to get the check. Even if they aren't expensing it, they make a lot more money than me and they invited you.
Back from lunch! The president of the company came and he paid. We just went to panera (my first trip to panera ever) and president made it clear to the checkout people that he was paying for all of us.