The US Code of Federal Regulations 33 CFR 151.1512(b) or 151.2035(b) define "original compliances dates" where vessels have to establish a "Quantitative Ballast Water Discharge Standard". All vessels are then required to be fitted with a type approved ballast water treatment system. Until a system receives full type approval from USCG, they can either install and use a system with AMS approval, or seek an extension from USCG. The implementation dates depend on vessel's construction date and ballast water capacity.
For example: Ships constructed before 2013, having a ballast water capacity of 1500-5000 m3 have to comply at the date of first scheduled dry docking after 2014! For more details refer to following information: