IMHO the whole point of collecting data is to know the truth about something. If you are changing archives to mislead someone then, unless your motive is to directly save people's lives, it's no different than lying. But, if you're changing data because it misrepresents the truth in its archived form, then by all means. Say for instance, a CEO authorized the entry of false data into the database in order to make himself/herself look better. Years later, from his/her jail cell the CEO confesses that he added 10% to his/her market research numbers. I don't see any problem with going back and adjusting the data so that it would now accurately reflect what it was intended to reflect. You could always just delete the data, but, assuming you trust the jail cell confession, it's possible it could still be usable.