Metaphor for conflict of interest

I'd like a metaphor/allegory which depicts a situation where one is compelled to not act. As an example (of such a situation), a company CEO, surrounded by and probably partial towards protecting certain parties accused in a company scandal and obviously partial towards protecting company image, being appointed to investigate the scandal.

Although the 'fox in the henhouse' metaphor is sometimes used to refer to conflicts of interest of all kinds, the situation it depicts is one where the fox is compelled to act (eat the chickens!) rather than not act, so it doesn't fit very well with the idea in that sense, and the result is that when translated into other languages the meaning gets lost (or inverted).

Solution 1:

The analogy/idiom is usually a variant of "That's letting the fox guard the henhouse," and I think it aptly fits the situation you describe: The fox is put into a position where it can determine an outcome that it desires. Whether the outcome is negative or positive is irrelevant to the point the analogy/idiom is making.