In many organizations, it’s this factor that sets real limits on what the organization can offer a new hire. Unless you’re coming in at a higher level than attorneys already on staff, you should not expect to be offered a salary that greatly exceeds the range of existing salaries.
While it’s not always possible or practical to get this information (e.g., what if there’s only one other attorney in the department), there is nothing wrong with asking what the range is if there are a number of assistant general counsels in the department. The general counsel salary can vary.