Need help writing trigger to only allow certain users to update/delete based on JOINED tables

Question

I have two tables, let's just call them A & B, which can be joined together via a foreign key. There is a BIT field on Table A (and only on Table A ), and once set to TRUE, I want ONLY users of a certain group membership to able to update/delete the record.

For just Table A, I used the following:

CREATE trigger [trigger_TableA] on [TableA] after update, delete
as
begin
set nocount on
 if exists (select 1 from deleted d where d.[BitFlag] = 1)
     and exists (select 1 from inserted i where i.[BitFlag] = 1)
     and 1 != isnull(IS_MEMBER('GROUP_NAME'), 0)
 begin
     RAISERROR('Only members of GROUP_NAME are allowed to update or delete.', 16, 1)
     ROLLBACK TRAN
  RETURN
 end
end

How would I modify the above for table to be a Trigger for Table B that involves checking the BitFlag on Table A?

Thanks!

Answer 1

 if exists (select 1 from deleted d INNER JOIN tableA a on d.? = a.? where a.[BitFlag] = 1) 
     and exists (select 1 from inserted i INNER JOIN tableA a on i.? = a.? where a.[BitFlag] = 1) 

Of course you will have to replace the ?s with whatever field you need to join on.