Social media have revolutionized communications by empowering millions of citizens to leap over traditional barriers and enter the public policy debate. But even in the brave new world of social media, there are still limits to who gets to speak and what they get to say.

Some of these limits are a matter of basic morality. And some are a matter of federal law.

Unfortunately, Twitter is brazenly disregarding these limits.

Twitter must certainly recognize that not everyone is entitled to the privilege of a Twitter account. If a Mexican drug cartel used the site to brag about its latest mass beheadings, I suspect that Twitter would shut them down. And if a pedophile took to Twitter to describe his latest conquests, I’d pray that Twitter would stop him cold.

So why is Twitter allowing a terrorist group with American blood on its hands to operate freely on its service?

During the recent conflict between Israel and Hamas, it came to light that the military wing of Hamas – the Ezzedeen al-Qassam Brigades – was operating a twitter account (@AlqassamBrigade).

These terrorists used this service to threaten Israeli civilians and brag about the missiles they fire at Israeli population centers.

More than 30,000 members of Christians United for Israel have emailed Twitter, asking it to ban Hamas. But Hamas tweets on.

Let me be clear. The account we are seeking to take down is not one operated by law-abiding citizens who sympathize with Hamas. Such independent advocacy is clearly and completely protected by the First Amendment. What we are talking about here is a page run by the terrorists themselves.

If shame is not sufficient to change Twitter’s behavior, then hopefully the law is. The fact is that allowing Hamas or any affiliated entity to operate a Twitter account is a violation of federal law.

The United States government has designated Hamas as a Foreign Terrorist Organization. Under 18 U.S.C. 2339A, it is illegal for any U.S. company to provide “material support” to such an organization. This prohibited material support specifically includes “services” and “communications equipment.”

By allowing Hamas to have an account, Twitter is providing it with an important “service” and extremely effective “communications equipment,” which are central to its primary mission of terrorizing the Israeli people and using civilian deaths to score political points.

In its February 2010 opinion in Holder v. Humanitarian Law Project, the United States Supreme Court stressed that it’s illegal to provide material support to terrorists even if such support is not directly linked to violence. In other words, the “services” that Twitter provides to Hamas violate the law, even if they’re not used to fire a missile or blow up a bus. The provision of these services is illegal even if it merely helps the terrorists brag about such attacks after the fact. As Chief Justice John G. Roberts Jr. wrote on behalf of the majority: “Material support meant to ‘promote peaceable, lawful conduct’ can further terrorism by foreign groups in multiple ways…. Such support frees up other resources within the organization that may be put to violent ends. It also importantly helps lend legitimacy to foreign terrorist groups – legitimacy that makes it easier for those groups to persist, to recruit members and to raise funds – all of which facilitate more terrorist attacks.”

In addition, I would note that murder and maiming are not the terrorists’ ultimate goal. They seek to use this bloodshed to “terrorize” a population into submission to their will. Thus threatening and communicating their attacks are central to the terrorists’ mission. A widely read tweet extends the range of the terrorists’ bomb.

Thus far, the Obama administration and the United States attorney’s office in San Francisco have maintained complete silence on this issue. This is a missed opportunity to take a strong moral stand against terror. Forcing Twitter to ban Hamas respects and reinforces what must be a bright red line between those who target civilians in pursuance of their politics and those who do not.

Rep. Ted Poe, R-Texas, has taken a leadership role in calling on the Obama administration to enforce our anti-terror laws and force Twitter to do the right thing.

I applaud his activism. And on behalf of our more than 1.2 million members, I call on his colleagues to follow his lead.

David Brog, the executive director of Christians United for Israel, is a former staff director of the Senate Judiciary Committee.