WASHINGTON -- Congress was on the verge of another big mess in early March of 2013. After months of posturing and negotiating, a self-inflicted shutdown seemed all too probable, with funding for the federal government expiring in just a few weeks.

That time, lawmakers managed to accomplish what just about every Congress has been able to do as a matter of course over the past century, securing a funding bill to (temporarily) keep the government running. But the high-stakes wrangling obscured another momentous event: the House GOP's dawning obsession with a meaningless rider that targets government-funded pornography habits. The final funding deal included the following passage no less than three times:

"None of the funds made available in this Act may be used to maintain or establish a computer network unless such network blocks the viewing, downloading, and exchanging of pornography."

Alas, the anti-porn language is unnecessary and essentially unenforceable. It can't actually change bureaucratic behavior.

Plenty of people are annoyed or angered by the prospect of government workers watching porn on the job. But federal agencies have been using anti-porn filters for years. And there is no evidence that any of the federal agencies targeted by the triplicate rider has taken action in response to it.

The actual language of the rider doesn't even specify what people using federal computer networks shouldn't be able to view. The term "obscenity" is vaguely defined in federal law, but the word "pornography" is not. The closest things have come is Supreme Court Justice Potter Stewart's famous "I know it when I see it" concurring opinion from 1964.

"It's just a layperson's term," said James Tyre, special counsel with the Electronic Frontier Foundation. "It's not a legal term."

In other words, if some anti-porn crusader tried to enforce the rider in court, the court would have to wade through a jurisprudential swamp to determine its legal substance. And that is assuming the case wasn't simply thrown out first. In order to sue the government over the rider, a private citizen would need to show that he or she had been personally harmed by its lax implementation. That would be quite difficult.

"Just because you contribute to the federal coffers as a taxpayer doesn't mean you can bring lawsuits [challenging the government's implementation of a specific law]," explained Tyre. "You have to show some other higher level of harm, and I'm not sure that you could."

Yet over the last 18 months, this pointless provision has spread like legislative kudzu into bill after appropriations bill.

Congress is making a habit out of empty boilerplate. House Republicans have voted more than a dozen times in recent years to block funding for the Association of Community Organizations for Reform Now, even though the group, better known as ACORN, closed up shop in early 2010. Similarly, in 2005, Republicans pushed a new rider blocking the use of any funds to change the oath of allegiance recited by those seeking to become naturalized citizens. That measure has since become standard in any legislation funding the federal government, despite no signs of any effort anywhere in any administration to change the oath.

While Republicans brought the porn rider to fruition, it was actually dreamed up by Democrats -- Rep. Chet Edwards of Texas and Sen. Barbara Mikulski of Maryland -- in the summer of 2010. The Securities and Exchange Commission's inspector general had recently flagged nearly three dozen of the agency's employees and contractors for watching porn on government computers, resulting in eight resignations and a range of disciplinary actions. Edwards drafted a sentence requiring that government computers block porn. According to the SEC inspector general, the misbehaving bureaucrats had actually disabled filters in effect on their computers, a tactic that the porn rider would not combat in any way.

The Edwards-Mikulski language didn't make it into law until after the GOP retook control of the House. Rep. John Culberson (R-Texas) slipped the exact same sentence into a 2012 appropriations bill that covered the Department of Veterans Affairs. In March 2013, with the six-month spending bill to avert a shutdown, the provision spread to the departments of Commerce, Justice and Homeland Security.

An omnibus spending bill in 2014 added the Department of Health and Human Services and the National Institutes of Health to the list of affected agencies. Since then, the anti-porn rider has shown up in two more bills that have passed the House and another that has yet to see a floor vote. So far, four of the 12 appropriations subcommittees have embraced the language, giving the rider plenty of room to spread its toothless terror.

The measure also is being adopted by legislators who seem to think it can accomplish something, prompting concern from free-speech advocates. When the language hit the NIH in 2014, the Electronic Frontier Foundation argued that it was a backdoor effort to kill off grants for online HIV prevention work that had been ridiculed by anti-gay groups. The provision could impede additional government operations involving health, crime and other areas that touch on human sexuality, EFF warned, since porn filters are notorious for over-blocking websites.

A spokesman for Rep. Jack Kingston (R-Ga.), who chairs the House Appropriations subcommittee covering HHS and NIH, told HuffPost that the HIV research grant was indeed the reason why the rider was added.

"The rider is to prevent wasting taxpayer dollars on frivolous and objectionable studies that do not fit the NIH's basic scientific research mission," said Kingston spokesman Greg Dolan. "Using the scientific method to determine website marketing best practices does not qualify as 'science.'"

But Kingston's efforts have been in vain. The University of Minnesota researchers responsible for the HIV prevention work are still receiving NIH funding, according to an NIH spokeswoman. Perhaps that's because the researchers didn't actually create a porn site. They did, however, attempt to educate gay men about safe sex, using such methods as a computer game mimicking "Space Invaders" with a penis-shaped blaster gun.

Culberson, who chairs the appropriations subcommittee that covers the VA, and Rep. John Carter (R-Texas), who heads the Homeland Security subcommittee, both declined to comment for this article, as did a spokesperson for the House Appropriations Committee. A spokesman for Rep. Frank Wolf (R-Va.), who chairs the Commerce and Justice appropriations subcommittee suggested that the language had been kicking around Congress for some time. Spokespersons for the VA and NIH noted that each agency already uses porn filters.