__init__.py

# There should only be a few permissions across your whole application.
permissions = {
    'view': 'view',
}


class RegContextFactory():  

    @property
    def __acl__(self):
        if self.base != 'x':           
            return [
                DENY_ALL
            ]
        else:
            return [
                (Allow, 'g:users', permissions['view']),
            ]

    def __init__(self, request):
        self.request = request
        # This essentially is used to create 2 contexts,
        # one for base == x and one for base != x.
        self.base = self.request.matchdict.get('base')

class RegCustomView():    

    def __init__(self, context, request):
        self.context = context
        self.request = request

    def full_reg(self):
         return Response('ok')

config.add_route('full_reg', '{base}/reg/{id}/full', factory=RegContextFactory)
config.add_view(view=RegCustomView, attr='full_reg', route_name='full_reg', request_method='GET', 
    permission=permissions['view'])