Is a port scan illegal?

Related questions

1. What is TCP Xmas Scan?
2. What port does UDP use?
3. How does a port scan work?
4. Why is port scanning illegal?
5. Which protocol does Ping use TCP or UDP?
6. What is TCP FIN scan?
7. What is Zoomeye?
8. What is TCP null scan?
9. What is port scanning using nmap?
10. What is a TCP port scanning attack?

Tags

1. #however
2. #civil
3. #permission
4. #trouble
5. #lawsuits
6. #without
7. #illegal
8. #system
9. #owner
10. #while
11. #person
12. #exists
13. #federal
14. #scanned
15. #performed
16. #scanning
17. #legal
18. #explicitly
19. #vulnerability