It should probably be claimed as extortion, but I haven't studied Cyber Law (yet).
There's no direct cyber law related to this kind of extortion (that I'm aware of, but there are of course other laws to protect people from extortion), but let me just check my notes..
U.S. Code Title 18, §1362: Communication lines, stations or systemshttp://www.law.cornell.edu/uscode/usc_sec_18_00001362----000-.html
U.S. Code Title 18, §2701 et seq: Stored wire and electronic communications and transactional record access.
(If the hacker has acquired access to data which he is not the intended recipient of.)
U.S. Code Title 18, §1029: Fraud and related activity in connection with access devices.
(If he has gained unauthorized access to a system.)
Most prosecutions in the USA goes into the U.S. Code Title 18, Section 1029 and 1030 (Fraud).
These only applies to the United States of course, and these are not all the laws that may apply in this case, but just a few of the common cyber laws.
A website that may interest you: http://www.cybercrime.gov//
Side-note: Mother of god, I should've never begun reading my notes, now I want to read all of them to catch up on topics I apparently forgot about xD
Extra Side-note: In case you wonder why I have these notes, you need to know about common cyber laws in various countries if you're going to do the GPEN certification. Other certifications such as CEH includes cyber laws too.