Unmanned aerial systems (UAS, or drones) could be used by malicious actors to conduct unauthorized surveillance or to deliver hazardous payloads within the United States. But defending against such threats may violate the law as currently written.
“Some of the most promising technical countermeasures for detecting and mitigating UAS may be construed to be illegal under certain laws that were passed when UAS were unforeseen,” the Department of Defense said in its legislative proposals for the FY 2018 defense authorization act. “These laws include statutes governing electronic communications, access to protected computers, and interference with civil aircraft” …
https://fas.org/blogs/secrecy/2017/06/drone-counter/
Secrecy News | June 13, 2017