XACML would be considered to be a “Voluntary Consensus Standard (VCS)” (aka an “open standard”) according to OMB Circular A-119, the authoritative federal mandate on this topic. WS-Policy and WS-Trust, however, would not be considered VCSs.
It is important to understand the difference between a standard and a specification – imho, standards are created in organizations (such as OASIS, W3C and Liberty) whose membership is open to all. Non-standard Specifications on the other hand, are created by consortia of vendors outside standards bodies such as the above. That’s not to denigrate their usefulness in any way, but the difference in process can be significant – open standards level the playing field; in contrast, you can never be sure whether a multi-lateral specification favours the members’ products. In fact, it would be somewhat irrational if it did not.