Capability-based access control is fascinating. Here's an interesting article about capabilities vs. ACLs: <a href="http://www.erights.org/elib/capability/duals/myths.html" rel="nofollow">http://www.erights.org/elib/capability/duals/myths.html</a><p>I'm also a fan of Macaroons for this purpose, which I was disappointed to see weren't being used here. But for an example of using macaroons as capabilities in practice, see: <a href="http://hackingdistributed.com/2014/11/23/macaroons-in-hyperdex/" rel="nofollow">http://hackingdistributed.com/2014/11/23/macaroons-in-hyperd...</a>