There is an expectation of privacy in the United States, and currently drones are in a legal grey area where case law hasn’t really been established yet.

https://en.m.wikipedia.org/wiki/Expectation_of_privacy_(United_States)

This is why the the ACLU recommends the following safeguards:

Usage Limits: A drone should be deployed by law enforcement only with a warrant, in an emergency, or when there are specific and articulable grounds to believe that the drone will collect evidence relating to a specific criminal act. Data Retention: Images should be retained only when there is reasonable suspicion that they contain evidence of a crime or are relevant to an ongoing investigation or trial. Policy: Usage policy on drones should be decided by the public’s representatives, not by police departments, and the policies should be clear, written, and open to the public. Abuse Prevention and Accountability: Use of domestic drones should be subject to open audits and proper oversight to prevent misuse. Weapons: Domestic drones should not be equipped with lethal or non-lethal weapons.