NFL Commissioner Roger Goodell sent a memo about Los Angeles to the league’s 32 teams Friday -- one that surely resonated with the San Diego Chargers, Oakland Raiders, St. Louis Rams and any others that might be considering relocation to the nation’s second-largest market.

“Although substantial uncertainties remain,” Goodell wrote in the two-page document obtained by The Times, “stadium development in Los Angeles has advanced to the point where the prospects for a new facility are better than they have been in many years.”

The purpose of the memo does not appear to be driven by any plans that might be imminent. Rather, NFL insiders say, the commissioner felt it was appropriate to set and restate some ground rules, foremost among them:

It’s the league -- and not an individual team -- that will control the relocation process.

In making that point, Goodell put in writing what was discussed by owners at a May meeting in Atlanta and established rules for moving back to a market that has been without an NFL franchise since the Raiders and Rams left after the 1994 season.

That the memo refers specifically to the 2013 season does not necessarily mean the league is ready to reenter the market immediately, but it does underscore how seriously the NFL is considering the current opportunities. In order to be considered for relocation, Goodell wrote, a team must submit its application to do so between Jan. 1 and Feb. 15 of 2013.

What the league doesn’t want is a team making the unilateral decision to relocate to L.A. intending to play in the Rose Bowl or Coliseum for a few years with the hope of moving over to a new venue once a stadium solution is found. The guidelines are partly intended to discourage squatting on the market.

Among the relocation candidates are the Chargers, Raiders, Rams and Jacksonville Jaguars, although new Jaguars owner Shad Khan has said he’s committed to staying put. At this time, the league is not considering expansion.

Raising the long-held league belief that L.A. is a two-team market, Goodell wrote: “Consistent with our long-standing view, we have made it clear that any stadium seeking investment support from the 32 member clubs should preserve a viable option of being able to host two teams at appropriate times and on appropriate terms.”

Goodell specifically made reference to the AEG proposal in downtown L.A. and Ed Roski’s concept in the City of Industry. He said the competing plans both have the ability to include ancillary entertainment opportunities such as a hall of fame, NFL Network studio, youth football facilities and the like.

Goodell wrote: “We are also exploring the availability of other sites in the Los Angeles area.” Those sites are believed to be in Carson, near Dodger Stadium and at Hollywood Park, where proposals have been pitched in years past.

Goodell wrote that issues such as approval to relocate, assessment and terms of a relocation fee, financial commitments from the league for stadium construction, and Super Bowls awarded must come from the full membership of teams.

Any such approval would require a three-quarters vote of membership, or at least 24 teams.

According to the guidelines, a team that intends to relocate must:

Negotiate a deal with an alternative site -- in this case the Coliseum or Rose Bowl -- that can play host to games while a stadium is being built, and keep the league fully apprised of every step in the negotiations.

Submit within the first 11/2 months of 2013 an application to relocate. “If no application is received for the 2013 season,” Goodell wrote, “we will consider when and under what circumstances clubs may apply for consent to relocate in a future season.”

Evaluate all stadium opportunities in its existing market, and consult with league staff on those. Unstated by Goodell, but implied by the NFL, is that the Raiders, for instance, would have to explain why it would be more practical to relocate than share a stadium in Santa Clara with the 49ers.

Goodell wrote that any application to relocate will be acted on as soon as possible, but that it’s unlikely any vote would be taken before the annual meeting in March 2013.

John Semcken, who has worked closely with Roski on the Industry proposal, said Goodell’s memo does not change their approach moving forward.

“That seems to be a procedure that the league is putting on the owners,” Semcken said. “I don’t know that that affects anything that we’re doing. It seems like [the NFL is] starting to focus and put procedures in place, which is great. That’s fantastic for us. We’re ready to go and have been since October of 2009.”

AEG is focused on the environmental impact report for the downtown project and expects it to be approved by the end of the summer, spokesman Michael Roth said.

Said Roth: “As we have said throughout this process, we continue to keep the league apprised on all of our progress and developments, and we will continue to follow the lead of Commissioner Goodell.”

sam.farmer@latimes.com