Generally, you cannot use or permit use of your Government position, title, or any authority associated with your public office in a manner that could reasonably be construed to imply that Government sanctions or endorses a fundraising or other activity of a private organization or cause, no matter how worthy.
For example: You are speaking at a convention on the subject of the use of a new product to reduce the influence of extraterrestrials upon Earth's environment. You introduce yourself as a member of an advisory committee for a Government agency deliberating on the utility of this very same product. Your speech might be construed an official endorsement of this product.
