A federal law, 12 U.S.C. 1790b, provides protection for credit union whistleblowers in certain situations. The law reads as follows:
No insured credit union may discharge or otherwise discriminate against any employee with respect to compensation, terms, conditions, or privileges of employment because the employee (or any person acting pursuant to the request of the employee) provided information to the [National Credit Union Administration] Board or the Attorney General regarding any possible violation of any law or regulation by the credit union or any director, officer, or employee of the credit union.
The law applies to specific types of reports, the "possible violation of any law or regulation by the credit union or any director, officer, or employee of the credit union," made to two specific entities (1) the Board of the National Credit Union Administration; and, (2) the Attorney General of the United States. It's clear what the NCUA Board is but whether a report to an agency or branch of the United States Department of Justice or other person short of the actual Attorney General will have to be decided by the courts.
You can learn more about legal protections for a credit union whistleblower at the Kentucky Employment Law Blog by Robert Abell: What Must A Credit Union Whistleblower Prove In a Retaliation Case?