Amazon's decision to boot conservative chat site Parler from its hosting platform, on the heels of Twitter and many other services banishing President Trump, brings three decades of hot argument over online speech to a boil.

Why it matters: Four years of a president who behaved like a boundary-pushing online troll, fostering mayhem that culminated in Wednesday's assault on the Capitol, finally forced the executives who control today's internet to draw lines.

Driving the news: Amazon said Parler, a social network that invites users to "speak freely and express yourself openly, without fear of being 'deplatformed' for your views," was failing to obey the company's terms of service by failing to remove "posts that clearly encourage and incite violence."

• Numerous examples of those have flooded the online conversation.
• After Parler backer Dan Bongino had posted a complaint against "the totalitarians at Apple and Google" (who had pulled Parler from their app stores), a Parler member posted, "It would be a pity if someone with explosives training were to pay a visit to some [Amazon] data centers."

Context: Every online business, from consumer-level apps down to infrastructure-level services, has a terms of service (TOS) that bars users from breaking the law.

• Giant platforms have built extensive programs to root out crimes like child pornography.
• None of that has anything to do with the companies' much-debated liability shield (Section 230) — a 1996 law that allows online providers to moderate user-contributed content without fear of being treated as a publisher responsible for every word.

Amazon, Apple and Google, in acting against Parler, maintain that they are simply enforcing long-standing rules.

Yes, but: They didn't do so before, and they're doing it right now — in the midst of a constitutional crisis triggered by an insurrectionary attack on the Capitol.

Be smart: No laws, and no terms of service, are every fully enforced.

• Enforcers always have limited time and resources, and choose who and what to go after.
• It's up to the rest of us to assess whether they are acting fairly and legitimately.

Amazon's move on Parler is momentous because Amazon's Web Services is more like a utility provider than a broadcaster.

• If you use the internet, you interact with AWS constantly, but you don't realize it, because Amazon is just providing the back-end computing power to run other apps and services.

The Parler crackdown, according to many on the right as well as some on the libertarian left, is fundamentally different from efforts to ban individual accounts on social networks for misbehavior.

• They say it's less like booing a speaker off the stage than cutting off the electricity to a building.
• There's precedent for it in network provider Cloudflare's decision to cut off 8chan in 2019 after the site after the El Paso shooting.

Between the lines: The most ambitious effort to date to try to define the infrastructure layer of the internet and provide special protections and obligations for providers of basic connectivity was a policy called net neutrality.

• Trump-appointed Republicans at the FCC ended that Obama-era policy.

Our thought bubble: You can view this debate through three different lenses.

• Freedom: Parler's supporters say their freedom of speech is being curtailed. Amazon and other online services are also free to operate their businesses according to rules they set.
• Power: Parler claims a place in the internet's tradition of empowering individual voices. A handful of Big Tech firms and CEOs today wield vast and largely unaccountable power.
• Justice: A mob stirred up by a U.S. president — both relying on tech-provided services — tried to violently overturn the results of a U.S. election. Executives and employees at every company that serves as a public square are taking a fresh look at ways to prevent a repeat.