Drones weighing at least 0.55 pounds (250 grams) must once again be registered with the FAA if they are flown for noncommercial purposes under Part 101, the FAA Special Rule for Model Aircraft. President Donald Trump signed legislation Dec. 12 that restores the registration requirement for drones flown for hobby or recreation that had been struck down by a federal appeals court in May. (That ruling did not affect the requirement to register drones flown under Part 107, which applies to commercial operation of unmanned aircraft.)
Source: aopaDrone registration requirement returns