Relationship or Attribute-based Access Control packages?

Does anyone know of a good RelBAC or ABAC package that could be used with Meteor?

Basically, I’m working on a site that needs access control similar to what would be used by Meetup.com for example. Think people with relationships to groups and groups with relationships to groups that could allow them to inherit asset access and a wide array of assets with permissions highly variable depending on the user’s relationships to owners and disseminators of the assets. Role-based access control simply can’t cut it.

Any pointers?