On Monday, the Supreme Court overturned the 2011 conviction of Anthony Elonis, a Pennsylvania man who was sentenced to jail time for writing a series of threatening Facebook posts. In the posts, Elonis repeatedly wrote about killing his ex-wife, murdering an FBI agent, and even carrying out a school shooting—violent, targeted words that landed him a 44-month prison sentence in 2011.

But Elonis appealed the conviction again and again, arguing that in order for a threat to be punishable under criminal law, the court would have had to prove not that his posts could be perceived as threats, but that he had actually intended them as threats in the first place. And in its a controversial ruling, Monday, the Supreme Court decided he was right.

It's a decision which, according to Danielle Citron, a professor of law at University of Maryland and author of the book Hate Crimes in Cyberspace, upends how courts have ruled on these issues in the past and leaves many questions unanswered as to how they should proceed in the future.

"The Supreme Court basically just said nine courts of appeals are wrong," Citron says.

Until now, the consensus has been that a threat is punishable if a “reasonable person” would perceive it as a threat. That is what the jury that convicted Elonis was charged with determining. And with posts that read, “There's one way to love ya, but a thousand ways to kill ya/And I'm not going to rest until your body is a mess/Soaked in blood and dying from all the little cuts,” that part was pretty much no brainer.

But with this ruling, the Supreme Court says courts must now rewire their thinking to also consider the defendant's state of mind and whether he actually intended to do wrong. For Citron, this does not come as a surprise. The concept of mens rea, Latin for "guilty mind," is found through criminal law. That courts have not had to prove a defendant's intent in threat cases until now, is actually the exception, Citron says, not the rule.

"The question the jury has to wrestle with is not a bizarre thing," she says. "If you're going to be thrown into prison for any length of time, you’ve got to have some moral culpability."

Proving intent doesn't require proving that the defendant planned to follow through on the threat. It simply means proving that the defendant knew that by sending the message, he would be instilling fear in someone else. Still, the problem for prosecutors now is that proving an intangible thing like intent will make it much tougher to convict people like Elonis.

"It is a tougher standard," Citron says. "There’s no question about it."

Elonis, for one, said that the Facebook posts were rap lyrics, no different from the ones Eminem has written about killing his ex-wife Kim Mathers. The defense team could then argue that Elonis's intent was merely to vent about his failed marriage through rap lyrics, which he just happened to post on Facebook.

Citron is doubtful that argument would stand up if Elonis were retried, but the Supreme Court's decision makes that argument relevant, nonetheless.

Another issue with the ruling is that the court didn't say exactly what type of intent was necessary. In other words, it doesn't say whether the defendant has to specifically intend to threaten another individual, or whether it's enough if the defendant knows that another individual could feel threatened by their behavior, and chooses to do it anyway, which is known in legal terms as "recklessness."

"This failure to decide throws everyone from appellate judges to everyday Facebook users into a state of uncer­tainty," wrote Justice Clarence Thomas in a dissenting opinion.

But Citron says that despite the lack of clarity surrounding intent, this decision may help pave the way for other online harassment legislation, including bills that seek to criminalize revenge porn online. Now that drafters of this legislation know that the Supreme Court requires intent to be a factor in these criminal cases, they can write it into the statutes from the beginning, rather than having them struck down later on. "We're getting a clear message from the court that in criminal statutes, you’ve got to prove either some intent to harm or knowledge of wrongdoing," Citron says.

Still, Citron says it's important to remember through all of this that online threat cases are rare, despite the ever growing existence of online threats. That's partially due to the fact that these crimes go unreported, Citron says, and partially due to the fact that many victims, particularly domestic abuse victims, have lost faith in law enforcement. So while the Supreme Court's decision may make it harder to punish these criminals, that's a small issue compared to the huge number of them who are never brought to trial in the first place. "The one good thing," Citron says, "is the Elonis case has brought the issue of online abuse and domestic abuse into the conversation and consciousness in a way that’s been immovable before."