"There's absolutely no question spam can be regulated," Jaynes' lawyer, Thomas Wolf, told the Virginia Supreme Court. "The problem with Virginia's statute is that it attaches severe criminal penalties to unsolicited bulk e-mail of a noncommercial nature."

Wolf said anonymous speech is protected by the First Amendment. A person anywhere in the world sending anonymous political or religious e-mails in bulk could unwittingly break the law because some of the messages almost certainly would pass through servers in Virginia, he said.

But State Solicitor General William E. Thro said the law doesn't bar speech — it prohibits falsifying Internet routing and transmission information to electronically trespass on a privately owned computer network.

"There is no constitutional right to use the property of others to engage in speech," Thro said.

He said using unsolicited bulk e-mail to "commandeer" a privately owned computer network is akin to stealing a car to drive to a political rally.

Previous discussion of the case here.  I think the arguments are very much colorable.