As far as I know, only manufacturers are required to implement
HACCP - meat, poultry, fish, some eggs and juices as well. Restaurants are moving toward voluntary
HACCP which is often customer or audit driven. Certain restaurant practices require
HACCP (i.e.smoking or curing in-house) but this might vary (I am not clear on all the details). Schools implemented
HACCP plans last year but I am not sure how this was enforced. Many retail establishments (grocers) also use
HACCP.
Food safety is regulated on the national level only where it crosses state lines (in commerce). On the local level - which is where most restaurants operate - it is up to the state to recommend rules and local health departments enforce them. Because of this, there is a lot of variety in the local rules. I don't know of any state that has recommended mandatory
HACCP for food service.