What happens when the proverbial unstoppable force meets an immovable object? In Iowa City, it leads to an insufferable, endless debate about the proper age of bar patrons.

Last week, a pair of Iowa City bar operators — Martinis owner George Wittgraf and Union Bar manager Josh Erceg — submitted to the city a petition to reverse the 21-ordinance, which has barred 19- and 20-year-olds from Iowa City’s bars after 10 pm since 2010.

If the petition signatures’ validity is confirmed by the city, the City Council will be required to either to overturn the 21-ordinance on its own or put the matter before the voters this fall.

City Councilor Jim Throgmorton told The Daily Iowan that the council would be unlikely to act on its own to reverse the ordinance.

In all likelihood, this issue will be dragged before the people once again in November. For Iowa City residents, the resurgence of this tiresome debate means more months of yard signs, scare-mongering, and an inevitable deluge of meaningless statistics and secondhand anecdotes about downtown safety.

The petitioners should set aside their quest to do away with the ordinance. The current law should stand.

In 2010, when the ordinance was debated and ultimately passed in a popular vote, the debate centered largely on scaling back problem drinking by University of Iowa students. Some argued that the ordinance would reduce such drinking and general rowdiness downtown; others posited that the rule would simply decentralize the party scene.

The biggest efect of the 21-ordinance wasn’t any change to underage drinking habits, however, though some statistics indicate that problem drinking may be on the decline in Iowa City.

It was Iowa City’s bar scene that changed dramatically.

In the immediate aftermath of the ordinance, some bars — Vito’s, One-Eyed Jakes, and 808 Restaurant & Night Club — closed down. Wittgraf told the DI that the peak hours downtown have also changed.

“Whereas it used to get busy at 10, it gets busy at 6 or 7 on the weekends,” he said. “It really hasn’t changed number-wise, just time-wise.”

It is unsurprising, then, that the remaining opposition to the 21-ordinance is led by bar owners.

Letting underage students back into the bars past 10 p.m. would reinflate the late-night downtown population and — because the city’s zoning laws effectively prohibit the establishment of new bars downtown — the existing bars would reap the benefits.

These bar owners are, ultimately, asking the city’s permission to once again profit from underage patrons all night. Their request should be denied.

That is not to say that the 21-ordinance should not be subject to change.

In the past, the city has proven responsive to complaints about the ordinance. For instance, the city has lifted the curfew for underage patrons in the city’s music venues in response to complaints from the owners of those establishments.

Clearly, the city is willing to work with the town’s bar owners to amend current law and fix existing inconsistencies and inconveniences where it’s appropriate. While we take exception to the idea put forward by some city councilors that they effectively have the power to reward or punish businesses by easing or tightening these restrictions, such small-scale modifications are preferable to another protracted debate about downtown restrictions.

Let the 21-ordinance stand.