In a bitter campaign for the Florida State Senate this fall, incumbent Maria Sachs was pummeled with negative TV ads produced by the state Republican Party. One ad suggested that Sachs, a Democrat, had fraudulently billed taxpayers for limousine rides she had never taken. A second ad acknowledged that Sachs had used the car services, but attacked her for “rid[ing] in style” in “luxury limos” on the taxpayers’ dime.

Sachs says both allegations are false, and soon before election day she hired an attorney and threatened to sue the Republicans for libel.

Now, after winning re-election, she has gone further. Sachs recently introduced a new bill that would ban defamatory claims in campaign ads for state elections by outside spending groups such as super PACs and political party committees.

The “Truth in Politics” bill would extend an existing Florida prohibition on malicious falsehoods by candidates to the new players unleashed by recent court decisions, as well as traditional party groups like the one that sponsored the limo attacks. Groups found guilty of smears by a nonpartisan state commission could be fined up to $5,000.

“What I’m going after is committees who have sprung up with lots of money to play in our political campaigns,” Sachs said. “Now that they want to play in the game, they have to be subject to the same limitations.”

Sachs’ proposal represents one of the more striking responses to date to a phenomenon that bedeviled many journalists, watchdog groups, and even candidates during the 2012 campaign: the barrage of TV ads, many of them deceptive, aired by new political players who operate outside traditional standards for accountability. Even as TV and print newsrooms committed new resources to factchecking, media watchdogs such as the Annenberg Center for Public Policy and Free Press have called on broadcasters to take the additional step of refusing to air false claims by outside spending groups. Sachs’s bill would take the efforts to clean up the discourse to an even higher authority, by making some of these deceptions illegal.

Emphasis on some. More than a dozen states have statutes similar to the Florida law that Sachs seeks to extend to outside spending groups. But these laws can only prohibit lies told with “actual malice”—injurious claims made with prior knowledge of the claim’s falsity or reckless disregard for the truth. And to run afoul of the laws, a false claim must injure the reputation of a candidate, so deceptions about policy issues are in the clear. Strictly speaking, the laws do not ban lies but libels.

“The only thing we’re changing is that we’re bringing in the new political members of this game,” Sachs said of her proposal.

Still, Sachs’s proposal enters a volatile constitutional battleground. The deceptive ads that reformers have urged broadcasters not to air are protected by many of the same principles that safeguard the freedom of the press. And recent Supreme Court jurisprudence may place even the existing state laws in jeopardy. Both the court’s recent campaign-finance decisions and a 2012 ruling that extended free-speech protection to lies about military honors set precedents that could prove fatal even to “actual malice” prohibitions like Florida’s.

Some regulatory approaches seem to be on safer legal ground. In Ohio, a state commission assesses whether political ads have lied with actual malice and issues reprimands to guilty parties. These public reprimands were upheld by the United States Sixth Circuit Court of Appeals, even as cease-and-desist letters and fines issued by the commission were struck down as unconstitutional. Prohibitions on specific types of false claims, such as deceptions about how and when to vote, also appear to be on safe constitutional terrain.

The broader legal questions, though, remain unsettled. “Courts have split on the constitutionality of some aspects of these false campaign ad laws,” said Richard Hasen, a law professor at University of California, Irvine who specializes in campaigns and elections. “I think eventually the issue will get to the Supreme Court.”

Sasha Chavkin covers political money and influence for CJR's United States Project, our politics and policy desk. He has written for ProPublica, the Center for Public Integrity, and The New York World. Follow him on Twitter @sashachavkin.