Could a beneficiary sue a pension fund for blatant breach of trust if it buys a bond with negative interest?

Sir I refer to Ralph Atkins’ and Elaine Moore’s “Negative rates to hit financial system”, February 16.

I have a question: Could a beneficiary sue a pension fund for blatant breach of trust if it buys a bond with negative interest? I mean is that not something like agreeing to a sort of prepaid pre-accepted haircut with somebody else’s money?

If I managed a pension fund, I would sure send a letter to all those who are expecting my management to provide them with a decent retirement stating something like: 

“Warning, we must inform you that central banks and governments are creating dangerously strange market conditions for which we hope you will not hold us personally responsible… and, for the time being, forget about expecting something like an 8 per cent return... if you earn enough with us to pay our costs, consider yourself a winner”.