sql DO in rule 9.0rc1 - Mailing list pgsql-general

Is there a technical limitation which prevents DO from being used in rules or am I missing something with this?

CREATE RULE test_update AS ON UPDATE TO test DO INSTEAD DO $$
                
                 BEGIN;
                                        
                 RAISE NOTICE 'hello';
                                        
                 END;
                                        
               $$;

Cheers,
M