Will a back surgery you had in 2001 disqualify you from being hired as a police officer?

It should not unless it prevents you from performing some essential job function or requires you to take medication that could impair you. There may be a concern over the potential for you to be re-injured, but that would certainly be decided by the individual agency. In short, as long as you can meet all relevent job duties, a past back injury should have no more impact than a past pulled muscle.