> I don't really buy using legislation. Alternatives exist and people don't seem to care to use them.

Google is engaged in using its market dominance in one segment to gain or maintain dominance in others, while suppressing the competition. This is illegal behavior for which Google has been fined several times over the past few years.

Just consider that in past Android versions there was a hard-coded Google search bar on the default home screen that you could not remove. Google has been forced to ask users and offer a set of alternative search engines on devices with recent Android versions. Same goes for Chrome and competing browsers [1].

Right now Google Search detects the Firefox for Android user agent and serves a second-tier search experience for Firefox users on Android. They have been doing this for the past 6 years [2].

[1] https://mashable.com/article/google-browser-search-engine-ch...

[2] https://bugzilla.mozilla.org/show_bug.cgi?id=975444

How is Google stopping users from using another search engine?

Once you have monopoly power, the market can do little. Google has that power now.

You mean like the power of yahoo/altavista back in the day?

You mean like when the internet was small and being on top of yahoo/altavista search results was mostly irrelevant to your bottom line?