Subsumes doesn't work when given user-minted privileges

[alejandrorusso]

The method subsumes for label objects does not return an appropriated answer when giving a user-minted privilege.

var p1 = new FreshPrivilege() ; 
var p2 = new FreshPrivilege() ;
var land = p1.asLabel.and(p2.asLabel) ; 
// The next instruction should return true but it returns false 
p1.asLabel.subsumes(land, p2) ;

However, it works if we write a similar code but using regular labels (and privileges),

var l2  = new Label ("http://bob.com:9090") ; 
var land = l2.and(COWL.privileges.asLabel) ; 
// The next instruction returns true
l2.subsumes(land,COWL.privileges) ;