Yeah, now that we're trying to bake this into ALTER TABLE we need to be a bit more cautious. I'd think:
ALTER TABLE tab POLICY ADD ...
Would work though? (note: haven't looked/tested myself)
Yes, I just tested it and the following would work from a grammar perspective:
ALTER TABLE <table_name> POLICY ADD <policy_name> (policy_quals)
ALTER TABLE <table_name> POLICY DROP <policy_name>
Though, it would obviously require the addition of POLICY to the list of unreserved keywords. I don't suspect that would be a concern, as it is not "reserved", but thought I would point it out just in case.
Another thought I had was, would we also want the following, so that policies could be modified?
ALTER TABLE <table_name> POLICY ALTER <policy_name> (policy_quals)