The Association of College and Research Libraries (ACRL) Framework for Information Literacy for Higher Education says: "Information resources reflect their creators’ expertise and credibility, and are evaluated based on the information need and the context in which the information will be used. Authority is constructed in that various communities may recognize different types of authority. It is contextual in that the information need may help to determine the level of authority required."
What does this mean?
Authority is constructed by society in the fact that we, as a society and culture, have decided who to give authority to, based on how our societies and governments are structured. This goes back to how our society is created for the division of labor. Rather than everyone doing everything, we specialize and become experts in certain fields and professions while allowing others to become experts in other professions. This allows people to become experts or authority figures in their own areas, but also requires us to give trust and recognize people as authority figures in their respective areas. This is how authority is constructed. There are certain rules established by society and our own disciplines that give authority to people. These rules could be an election to give authority to a person to be the president, or a set of processes and requirements to give someone intellectual authority through a degree. The school and university systems are all ways we have constructed to establish authority.
This also highlights how authority is contextual. Because we have divided the labor, we are all only experts in our respective areas. For example, not all doctors are created equal. You wouldn't want to get heart surgery from a dermatologist. Someone with a Ph.D in Sociology is not necessarily qualified to teach Biology, and so on. A doctor of philosophy cannot do what a doctor of pharmacology can. How much authority someone has depends on the context.
Authority is also constructed and contextual through a combination of both the book learning, such as getting a degree, and practical knowledge, which is the experience. Someone with years of experience in the field would be considered more authoritative than someone freshly graduated from college. However, that is only if they have continued to expand their knowledge and stay up to date and certified. There is also more nuance since some professions don't require a degree, although it's certainly a bonus. So how would you compare a software engineer who has 10 years of experience but no degree to a freshly graduated computer science major who has no experience? Which one is more authoritative?
Authority is further contextual in the realms of where the authority comes from. Political authority is different from intellectual authority, and then we have levels of cultural authority through traditions, such as religion and social structures. An example of this is the authority of a leader of a church. People who join that church accept the authority of that leader through their belief. If they don't believe or aren't a member of that church, then they don't technically have authority over them. Social structures, such as the family, will dictate that parents have authority over children, and that elders have authority over youth based on their years of experience, and so on. Each type of authority is based on the context or situation, and won't have the same authority in a different context. It also shows the construction of that authority through the construction of the cultural norms.