Under league bylaws, a move needs approval from at least three-fourths of the owners. They must consider public financial support and the condition of a team’s current stadium, as well as “the willingness of the stadium authority or the community to remedy any deficiencies in or to replace such facility.”

Mayor Kevin L. Faulconer of San Diego, like his counterparts in Oakland and St. Louis, knows those rules well. To convince the N.F.L. that the city wants the team to stay, he assembled a task force that recommended that a stadium be built next to the Chargers’ current home on city-owned land in Mission Valley. He helped speed up an environmental review so a public vote could be scheduled for January.

After more than a decade of false starts, the Chargers say they do not have time to wait for the city to get its stadium approved because the Rams are intent on moving to Los Angeles and grabbing a chunk of the Southern California market. Rather than get caught up in what they consider the city’s unworkable efforts, the Chargers walked out of discussions in June.

“We’ve been trying for 14 years in San Diego, and unfortunately the city’s 11th-hour proposal is simply too little, too late,” said Mark Fabiani, the Chargers’ special counsel. “The Chargers can’t stand idly by and pass on a certain opportunity in the L.A. market while the city of San Diego insists on a plan to skirt California’s environmental laws that will ultimately be thrown out by the courts.”

Frustrated, the city has gone around the team.

“We have all the resources in San Diego, and that’s why we’re taking our case directly to the N.F.L.,” said Faulconer, who has spoken to Commissioner Roger Goodell and others at the league office. “Make no mistake: You can’t have a final plan without a willing partner. You can only achieve success if you work together.”

The dynamic in St. Louis is different. A group of civic leaders backed by Gov. Jay Nixon of Missouri has been working on a plan for a $998 million stadium downtown near the Mississippi River. Last week, the group passed a key hurdle when a judge ruled that the stadium authority could roll over its existing bonds to help pay for the new site.