table1.objects.exclude(id__in=
    table2.objects.filter(your_condition).values_list('id', flat=True))

The exclude function works like the Not operator you where asking for. The attribute flat = True tells to table2 query to return the value_list as a one level list. So... at the end you are obtaining a list of IDs from table2, which you are going to user to define the condition in table1, that will be denied by the exclude function.