Do Washington's net neutrality rules run roughshod over the First Amendment?

That's what some opponents have been arguing -- claiming that the government's regulations infringe on Internet providers' right to free expression. Now, in a flurry of responses to that charge, defenders of the rules appear eager for the biggest showdown over the meaning of corporate speech since the Citizens United case.

Internet providers and the Federal Communications Commission are entangled in a major district court battle over net neutrality, the government policy that earlier this year forbade Internet providers from selectively speeding up or slowing down Web sites. Agency critics are focusing their attack on an FCC decision to switch how it regulates companies like Comcast and AT&T. They argue the FCC went way beyond the powers laid out for it by Congress in what is essentially the agency's playbook, the Communications Act.

One obscure thread of this argument, though, claims that the FCC didn't just misuse its powers, but that the consequences of its decisions actually stifle Internet providers' rights to free speech. This is a big deal. If the Citizens United case was about whether corporations could "speak" with money, this latest fight questions whether broadband providers can be said to "speak" with Internet data.

"Broadband providers are First Amendment speakers because they 'engage in and transmit speech,'" according to a court filing by network engineer Daniel Berninger and Alamo Broadband, a small, Texas-based Internet provider.

Berninger and Alamo say that a carrier engages in commercial speech when it offers exclusive content and services to consumers over its networks. Meanwhile, they argue, carriers engage in political speech when they make decisions about what kinds of content to serve to their customers. Decisions by the government mandating what companies have to transmit are therefore unconstitutional, the critics say.

The FCC's rules "deprive broadband providers of their editorial discretion by compelling them to transmit all lawful content, including Nazi hate speech, Islamic State videos, pornography, and political speech with which they disagree," according to the brief, which also compares Internet providers to old-school newspapers and TV stations.

But legal scholars who defend the FCC say that is the whole point of net neutrality. Internet providers shouldn't be the ones to distinguish between acceptable and unacceptable content; their role is simply to transfer information without bias, wrote Zephyr Teachout, the New York-based law professor who ran for state governor in 2014. Joining her was Sascha Meinrath, founder of the Washington-based Open Technology Institute.

If the court allows broadband companies to shut off access to Web sites and ideas they don't like and funnel consumers instead to the sites and ideas that are favorable to corporate interests, "we risk loss of the free flow and exchange of ideas central to our democracy," the two wrote in a legal filing.

Others are challenging the idea that Internet providers are even capable of speech. As pipes that carry consumers' Web traffic to and fro, Internet providers are just a "conduit" for people's speech, according to a group of academics including Harvard's Lawrence Lessig and Yochai Benkler, and Stanford's Barbara van Schewick.

"It follows that when the Open Internet Rules require providers to carry others’ speech, they do not require the providers themselves to speak," they argue in their own brief.

What they're saying is that Internet providers don't really "speak" when they send your data whizzing across the Web — so there's no way the net neutrality rules really force them to say things they don't want to say. For the purposes of their core business, in other words, Internet providers are mute.

This back-and-forth over corporate speech has ballooned into a surprisingly substantial debate. If you'd asked me a few months ago whether this might happen, I would've been skeptical. At the time, the First Amendment allegation seemed like a secondary argument to the accusations that the industry was preoccupied with at the time, which were about narrow matters of agency process and FCC authority. But — perhaps in an attempt to cover all the bases — the FCC's allies have addressed the First Amendment issue head-on, and it's raising big questions about the role businesses play in our democracy.