The U.S. Supreme Court on Monday struck down rules allowing government debt collectors to use cellphone robocalls while banning all other groups using the same technique.

Six justices said the government carve out in a 1991 law broadly prohibiting robocalls to cell phones and home phones violates free speech protections of the First Amendment.

"Although collecting government debt is no doubt a worthy goal," writes Justice Brett Kavanaugh in the majority opinion, "the government concedes that it has not sufficiently justified the differentiation between government-debt collection speech and other important categories of robocall speech, such as political speech, charitable fundraising, issue advocacy, commercial advertising and the like."

Seven justices concluded that the provision should be invalidated but that the remainder of the robocall law still stands.

"The continuing robocall restriction proscribes tens of millions of would-be robocalls that would otherwise occur every day," Kavanaugh writes. "Congress's continuing broad prohibition of robocalls amply demonstrates Congress's continuing interest in consumer privacy."

The Trump administration had sought to uphold the so-called government debt exemption to the federal robocall ban in the interest of recouping more overdue funds.

A group of Democratic political pollsters who brought the case argued that the exception discriminated against their desire to conduct robocall polling.

The court's decision means the government or an authorized third party can no longer robocall Americans to collect on past taxes or other IRS debts but can continue to use real person calling and direct mail.

This report was featured in the Tuesday, July 7, 2020, episode of “Start Here,” ABC News’ daily news podcast.