AMNA NAWAZ: Welcome to the "News Hour."

In a landmark ruling, a federal judge has found that tech giant Google broke antitrust laws, acting illegally to maintain a monopoly in online search.

Google currently controls roughly 90 percent of the world's Internet searches.

Today's ruling could upend how Americans get their information online and fundamentally change the way that big tech companies operate.

To help explain what this all means, I'm joined now by Rebecca Allensworth, a professor at Vanderbilt Law School.

So, Professor, just put this into context for us.

How big a deal is today's ruling?

REBECCA ALLENSWORTH, Vanderbilt Law School: It's a really big deal.

The Biden administration has five major monopolization cases going right now against Google, Meta, Amazon and Apple.

This is the first one to go to trial.

And they won.

So, in a sense, they're one for one.

AMNA NAWAZ: So, when we take a step back here, we see the DOJ and states had sued Google a few years ago, accusing it of illegally securing this online search dominance we just noted in part by paying companies like Apple and Samsung to make sure Google was the default search engine on their devices.

Do they have to change that practice as part of the remedy here?

I mean, what changes with this ruling?

REBECCA ALLENSWORTH: Well, the judge didn't say anything about a remedy yet.

That's going to be the next round of litigation.

And we can expect both sides to fight hard over that.

But, yes, very likely there will be a remedy that changes the way that we engage with search on our phones and on our devices.

And it's hard to overstate what a big deal this is.

The Biden administration has been trying in lots of different ways to come after competition in the big tech sector, which it feels like is flagging.

And this is a real sign that antitrust is up for the task.

It's not stuck in the smokestack industries.

And depending on how the remedy comes out, this could be a really, really big turning point in how we think about competition for big tech.

AMNA NAWAZ: And are there broader implications here for big tech in terms of how they're currently operating?

Will any of that change as a result of this ruling?

REBECCA ALLENSWORTH: I think it will.

I mean, this case, of course, only applies to Google and we still have to see the remedy and then, of course, appeals.

But there's all kinds of, I would call them bread crumbs in the opinion that other litigants could take up in other cases against tech, lots of holdings here that are relevant to the cases that I mentioned before, but also any other challenges that you might have to how tech is competing.

I would be very concerned if I were thinking about how the competitive landscape is going to look in the future if I were a tech company.

I might not have the monopoly and the dominance that I have enjoyed for the last 10 or 20 years.

That's not going to be as secure after this case comes out.

AMNA NAWAZ: What are some of those bread crumbs as you put it?

What stood out to you about the details of the judge's ruling today?

REBECCA ALLENSWORTH: Well, first of all, he said that this is a zero price market.

Consumers don't pay for search, and yet that is not something that is a defense, that zero price markets can be monopolized.

Defining a market is a little bit difficult in a zero price context.

He doesn't have any problem defining a market here.

So I think a lot of the tools that the tech companies have been trying to use to combat other tech companies in other cases, have been trying to combat their problems, are becoming a lot more suspect after this case on the books.

AMNA NAWAZ: So you mentioned no remedy decided just yet, but should users of Google expect any kind of difference in how they interact with the search right now.

REBECCA ALLENSWORTH: Not in the short term.

I think the remedy will be months, if not years away.

And I do think that there's likely to be a difference in the way that we engage with Google ultimately, but not in the short term.

The big thing here is just the precedent that it sets for both Google, but also the rest of the tech companies and going forward in what they can and can't do.

What the rules of the road in big tech are is changed by this case.

AMNA NAWAZ: You know, you take a step back, on that note, the last big antitrust ruling against a tech company was more than 20 years ago against Microsoft.

We're in an entirely new Internet age right now.

So, when you look at this ruling in that context what does it say to you about the government's potential role when it comes to regulating tech companies.

REBECCA ALLENSWORTH: Well, the government has always had a major role in regulating competition.

That goes back to the Sherman Act from 1890.

What's really unusual is how it has abdicated that role over the last 20 years.

And I think this is a turning point in that story.

I think that this does say that the government has an important role to play even in emerging and networked tech industries.

AMNA NAWAZ: That is Vanderbilt Law School's Professor Rebecca Allensworth joining us tonight on this landmark Google ruling.

Professor, thank you.

We appreciate your time.

REBECCA ALLENSWORTH: Thank you.