Question

What caveat (warning) does Nixon give regarding his cooperation with the investigation?

Answer 1

Answer:

Unclear question. However I infer you are referring to US former President Richard W. Nixon.

Explanation:

His ploy was to issue a fake warning that the investigation is harmful to National Security.

Remember, the then President Nixon was under heavy investigation by the F.B.I so he warned that attempts to reveal the truth was going to endanger the country's security just to frustrate the investigations.