With which access control method do system administrators establish what information users can share?

Answer: Mandatory access control

Explanation:

Mandatory access control is defined as the highly uncompromising access control. This access control provides accessing resources of the system under surveillance of system administrator or operating system.

It does not permit access of any subject for operating or functioning on object without authority. It has the ability to manipulate the control through system administrator. It controls who can share information by accessing, what information can be shared, circumstance of access etc.