https://www.recode.net/2017/5/19/15663436/us-drone-registration-rules-faa

"The court ruled that the FAA’s drone registration rules, which have been in place since 2015, were in violation of a law passed by Congress in 2012. That law, the FAA Modernization and Reform Act, prohibited the FAA from passing any rules on the operation of model aircraft — in other words, rules that restrict how non-commercial hobbyist drone operators fly.

Now, if a person buys a new drone to fly for fun, they no longer have to register that aircraft with the FAA. But if flying for commercial purposes, drone buyers still need to register."