There is no government or outside agency or third party which monitors the trust. The trustee(s)  are in charge of making sure that the trust does what it's supposed to--that's the role of trustees. If the beneficiaries of the trust believe that the trustee(s) are either shirking their responsibility or actively taking money from the trust (or diverting assets to friends or families, or otherwise using trust assets for their own purposes), the beneficiaries can file a kind of legal action in county court traditionally called an action for an "accounting" (your state may have a different name for it) in which they ask the court to make the trustee(s) "account" for what they are doing. If the court finds the trustees are failing in or violating their responsibilities, the court can order that they do or not do certain things, repay monies to the trust, or replace them as trustees.