Keeping an ocelot is regulated by varying laws in the United States. While several states don't require permits to own this big cat, other areas, including New England and Alaska, specifically prohibit keeping ocelots as pets, according to Big Cat Rescue.
Ocelots are allowed in some areas and prohibited in others. As of 2014, some states "grandfather" these exotic animals in if the owners obtained them before a certain date, as spelled out in detail at Born Free USA's site. This source also lists a handy code for determining whether no license or permit is required at all to own an ocelot or whether more stringent rules apply. Some states allow ocelot ownership if they were legal in a former state of residence or if they're being used for scientific advancement or educational purposes. Even in strictly controlled areas, these cats may also be allowed if they're being fostered by humans because they cannot be returned to the wild. Even in those cases, however, there are usually limits on how many ocelots can be held by one owner.