The LaLiga president has previously said it will be "practically impossible" for Barca to make any signings this summer because they will be in excess of their league-imposed spending limit after this season.
Tebas warned Barca as recently as March that they must either cut from the wage bill or raise in transfer fees as much as €200 million to even consider being able to bring in new players.
However, although he won't change the regulations, he did change his tone slightly on Wednesday as he claimed Barca have the "capacity" to make the necessary savings to be able to afford Messi.
"As of today, no, but there is a lot of time left," Tebas said in a news conference when asked whether Barca could re-sign Messi. "We are waiting for their [financial fair play] viability plan [for next season].
"I hope they can make the necessary moves to make space for Messi to come in, but of course we are not going to change any rules for Messi to sign. Barca can make moves; they sell players.
"That's what we hope happens because I am a fan of Messi and I would like Messi to play in our league. But we won't change any rules. It is complicated, but I think they have the capacity to do it."
Barca also maintain an interest in bringing Messi back to Spotify Camp Nou, with vice president Rafa Yuste recently admitting there has been contact with the player's camp.
Tebas was speaking after LaLiga had held an extraordinary assembly, in part to discuss Barca's payments to the former vice president of the refereeing committee in Spain, Jose Maria Enriquez Negreira.
Barca president Joan Laporta said in a news conference on Monday that the club had never bought referees and that the money was for services relating to scouting and technical reports on refereeing.
"Laporta had 20 minutes to give an explanation, and it was more or less what he said on Monday," Tebas said of the Barca chief's speech at Wednesday's meeting in Madrid.
"We [La Liga and the other clubs in Spain's top two divisions] didn't interrogate him, but the club presidents had their chance to offer their point of view.
"It was all very well-mannered. Laporta insisted Barca never bought referees. The other clubs said that the payments are unusual and must be investigated. Laporta's explanation is not convincing.
"LaLiga can't look the other way on these issues. I don't think Barcelona bought referees, but there are indications the payments were intended to influence. Mere intent may be punishable."
Barcelona replied to Tebas in a statement on Wednesday, saying, "As a courtesy and out of respect for the professional clubs, the president [Laporta] provided the relevant explanations on this matter, and out of respect for the administration of justice, he stated that any clarifications and queries requested by LaLiga or the clubs after his explanations will be answered in court, where LaLiga has already presented."
Barca paid over €7m to companies linked to Negreira between 2001 and 2018. Prosecutors have accused them of buying favour from referees, and a Spanish court is investigating the matter, while UEFA have launched their own independent investigation.
LaLiga cannot take any action because of a sports law in Spain that prevents punishing anything that happened more than three years ago, but UEFA are not bound by such regulations.
Barca face potential expulsion from the Champions League for one season should UEFA proceed and determine there was wrongdoing.