What is the test for establishing a "clearly established" inquiry?

fact-specific inquiry." Id. On the other hand, courts must "apply the 'clearly established' rule in such a way that faithfully guards 'the need to protect officials who are required to exercise their discretion and the related public interest in encouraging the vigorous exercise of official authority.'" Id. (quoting Harlow v. Fitzgerald, 457 U.S. 800, 807 (1982)).