Q: At work, two departments have two separate requirements. One requires a four-year bachelor's degree with a lower starting salary than the other, which requires only a two-year associate's degree. Is this appropriate?
A: I know of no legal precedent requiring employers to pay someone with a bachelor's degree more than someone with an associate's degree. If your company has a compensation strategy that pays its employees based on competence and skill sets, it is possible that someone with an associate's degree would get paid more than an employee with a bachelor's degree.
I can't say whether it is appropriate to pay employees with an associate's degrees more than employees with a bachelor's degree because I don't know what jobs and departments you are referring to. For instance, some IT jobs that require only an associate's degree will pay more than some jobs in accounting.
Your company will only run into problems if it applies its policies inconsistently. It shouldn't require one employee to have a bachelor's degree, and pay someone without a bachelor's more money in the same position.