By U.S. federal regulation, pilots are the final authority regarding the safety of flight.
14 CFR 91.3(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.
14 CFR 91.3(b) In an in-flight emergency requiring immediate action, the pilot in command may dviate from any rule of this part to the extent required to meet that emergency.
14 CFR 135.19(b) In an emergency involving the safety of persons or property, the pilot in command may deviate from the rules of this part to the extent required to meet that emergency.
The bottom line is that no one — not the pilot’s employer, not air traffic control, not even the FAA — can overrule a pilot’s safety decision. The pilot might have to justify his decision after the fact, but during a flight, only the pilot can decide if and when it’s necessary to make a precautionary landing.