Imagine if Congress passed and the president signed a law making it a crime to utter “false, scandalous and malicious” statements “against the government.” Do you think that would violate your right to free speech?

Of course it would. It’s startling to realize that such a law was, in fact, enacted at one time. In 1798, to be specific. The Alien and Sedition Acts were signed by President John Adams, no less. If you can’t trust an actual Founding Father to oppose such an unconstitutional law, who can you trust?

Jump to 2014, and you’ll find the same impulse to quash speech we disagree with is alive and well. All that’s changed are the tactics. Frontal assaults are out. Today’s politicians are savvier about how they propose to limit speech.

Hence, Sen. Tom Udall, New Mexico Democrat, has introduced a constitutional amendment that would allow Congress to limit fundraising and spending on election campaigns.

It’s dressed up in rousing calls to get so-called “dirty money” out of politics. We need to “level the playing field,” proponents of Mr. Udall’s amendment insist. Their goal is purportedly to make it so rich donors can’t “rig the system” and “buy elections.”

Don’t fall for it. It’s a new way to play an old trick.

Supporters of the proposed amendment point out that the amendment says nothing about speech. Go talk all you want. You won’t be thrown in jail like those who violated the Alien and Sedition Acts, so what are you complaining about?

This is semantics, though. Free speech doesn’t just refer to the literal use of your voice. It’s a good thing, too, because how can you make your views known if you don’t spend money? Most Americans support the candidate they favor with a financial contribution, of course, but almost every other activity involved in campaigns calls for money, from printing brochures and signs to buying airtime for political ads.

In short, an essential part of your free speech is the ability to spend your money as you see fit to express your views. As Hans von Spakovsky, a former member of the Federal Election Commission, has written, “Bans on spending are bans on speech.”

That’s why the Supreme Court, in a landmark 1976 decision known as Buckley v. Valeo, struck down federal limits on campaign expenditures. Such limits, the court said, restrain “the quantity and diversity of political speech.” We need the broadest possible protection of speech to guarantee an “unfettered interchange of ideas for the bringing about of political and social changes desired by the people.”

More recently, the court struck down a federal ban on independent political speech by corporations, unions and associations. In 2010’s Citizens United v. Federal Election Commission, the justices called free speech “an essential mechanism of democracy” that is “the means to hold officials accountable to the people.”

Some incumbents don’t like challengers. They also don’t like the fact that voters can freely use their money to make their voices heard. So they’re pushing Mr. Udall’s amendment, which would not only give Congress the power to limit what you can contribute to candidates, but limit the amount that the candidates could spend on campaigns.

Worse, they’ve carved out exemptions for the media. “Thus, The New York Times and MSNBC could continue to spend as much money, newsprint and airtime as they want supporting their preferred candidates – or attacking those they oppose,” notes Mr. von Spakovsky. The rest of us would be out of luck.

Mr. Udall’s amendment is plainly an end-run around the Supreme Court, which has so far held the line on the First Amendment. “Virtually every means of communicating ideas in today’s mass society requires the expenditure of money,” the court noted in Buckley.

What was true in 1798 and 1976 remains true in 2014. Bans on money are bans on speech, and every American’s right to speak freely should be given the fullest protection possible under the Constitution. Limit campaign spending, and we’ll all pay the price.