Employers routinely instruct participants not to discuss an investigation. The scope of that instruction is constrained.

Labor law. Blanket confidentiality rules covering all investigations have been found to interfere with protected concerted activity. The current approach permits rules that are narrowly tailored, with a legitimate justification outweighing the interference, and employers should assess the need case-by-case.

Legitimate justifications. Witnesses need protection; evidence is in danger of being destroyed; testimony is in danger of being fabricated; there is a need to prevent a cover-up. Generalized concern about workplace gossip is not enough.

Duration. Limited to the pendency of the investigation, not indefinite.

Scope. The instruction should not prohibit discussing the underlying conduct, terms and conditions of employment, or communicating with government agencies. It should be limited to the substance of the investigation itself.

Anti-retaliation. Participants must be told they may raise concerns and that retaliation is prohibited, which is inconsistent with an instruction that reads as a gag.

Practical drafting. A short written statement given at each interview, requesting rather than commanding discretion, explaining why, and expressly preserving the rights above.