If you still have a traditional landline in California, a federal lawsuit filed this week is about whether that option survives at all.

AT&T filed suit Wednesday against California regulators, asking a federal court to declare that the company no longer has to offer copper-wire phone service to new customers. The company named the California Public Utilities Commission and the state attorney general as defendants. The commission did not respond to a request for comment.

What AT&T is arguing

AT&T says California currently forces it to spend roughly $1 billion a year maintaining a telephone network that almost nobody uses. By the company's own count, that network now serves just 3% of households in its California territory. For $1 billion a year, that is an expensive fraction.

Alongside the lawsuit, AT&T asked the Federal Communications Commission for permission to discontinue traditional phone service in parts of California where it says faster, more modern service is already available. It also asked the FCC to rule that California's maintenance requirements are overridden by federal standards, effectively asking Washington to settle the dispute over Sacramento's head.

In return, AT&T committed to investing $19 billion in California through 2030, promising to connect more than 4 million additional households and businesses to newer internet-based networks.

Why this fight matters beyond California

For most people, this looks like a cleanup operation on obsolete infrastructure. And in many ways, it is. The copper landline network is more than a century old. AT&T says California has already experienced about 2,000 outages this year from copper thefts alone, and that replacement parts are increasingly hard to find. Switching off the old network would save an estimated 300 million kilowatt-hours of electricity annually by 2030, equivalent to eliminating emissions from burning 17 million gallons of gasoline.

But the 3% who still rely on copper lines are not randomly distributed. They tend to be older residents, people in rural areas with spotty wireless coverage, and households that never switched because the old system simply worked. For them, the alternative AT&T is offering, an internet-based phone connection, depends on a working power supply. Traditional copper lines carry their own current from the telephone exchange, which means they keep working during a power outage. In wildfire country, that distinction is not a minor technical detail.

AT&T argues that the federal government and nearly every other state where it historically operated have already removed the rules requiring it to maintain copper networks. California is, by its account, the last significant holdout. If the courts or the FCC side with AT&T, California's ability to set its own infrastructure standards could be sharply narrowed, not just for phone lines but as a precedent for how much states can demand from carriers operating inside their borders.

If California wins, AT&T still has to spend a billion dollars a year on a network serving roughly one in thirty households, and its $19 billion modernization pledge may face continued complications.

The people most exposed to a bad outcome here are the ones least likely to be following a federal lawsuit. The shift from copper to digital phone service has been underway for years across the country. California held the line longer than most states. The lawsuit is, at its core, a dispute about who decides when that line finally ends.