In distributed transactional database systems deployed over cloud servers, entities cooperate to form proofs of authorizations that are justified by collections of certified credentials. These proofs and credentials may be evaluated and collected over extended time periods under the risk of having the underlying authorization policies or the user credentials being in inconsistent states. It therefore becomes possible for a policy-based authorization systems to make unsafe decisions that might threaten sensitive resources. In this paper, we highlight the criticality of the problem. We then present the first formalization of the concept of trusted transactions when dealing with proofs of authorizations. Accordingly, we define different levels of policy consistency constraints and present different enforcement approaches to guarantee the trustworthiness of transactions executing on cloud servers. We propose a Two-Phase Validation Commit protocol as a solution, that is a modified version of the basic Two-Phase Commit protocols. We finally provide performance analysis of the different presented approaches to guide the decision makers in which approach to use.