Short answer?
Maybe:
So will Apple and AT&T's legal action deter hackers? Hardly. Individual users are already allowed to unlock their own phones under an exemption to the Digital Millennium Copyright Act (DMCA) that the U.S. Copyright Office issued last November. The exemption, in force for three years, applies to "computer programs…that enable wireless telephone handsets to connect to a wireless telephone communication network, when circumvention is accomplished for the sole purpose of lawfully connecting to a wireless telephone communication network."
What's less clear is whether companies and hackers can legally unlock the phones and then sell them to others, or sell unlocking software. "The law here is unclear," says Jonathan Kramer, founder of Kramer Telecom Law Firm in Los Angeles. "There just isn't any case law in this area for us to figure out how it plays out."
Not very clear is it? In the end I don't think it matters that much. The real problem is, even if it
is legal, Apple can always deny support to hacked iPhones and the warranty is definitely void after this type of tampering. Because of the vast, insulting amounts of money involved, count on Apple and AT&T to get theirs one way or another.