The University of Michigan’s 10-page response to the Big Ten on Wednesday night sets the stage for an unprecedented legal battle between school and conference over a sign-stealing probe that has gripped college football.

In the letter, Michigan warns Big Ten commissioner Tony Petitti against what it describes as “premature” disciplinary action against head coach Jim Harbaugh, questions the league’s evidence in the case as grossly insufficient, and believes the conference is in a “rush” to punish the Wolverines because of public and internal pressure from other Big Ten schools that would create an “indefensible precedent.”

Yahoo Sports obtained a copy of the letter, which includes two attached documents of Michigan's offensive and defensive signs allegedly stolen and shared by other Big Ten teams.

In the letter, signed by Michigan athletic director Warde Manuel, the university suggests that sign-stealing is a rampant and somewhat common practice and the school fires a warning at its own league: “The conference should act cautiously when setting precedent given the reality that in-person scouting, collusion among opponents, and other questionable practices may well be far more prevalent than believed.”

Michigan’s response was an expected next step in the league’s case against the program over a sign-stealing scheme that spans dozens of games and at least three years. Petitti is now expected to rule on the matter. The commissioner is considering a multi-game suspension for Harbaugh, something he suggested to Michigan officials in a meeting Friday.

As their letter proves, president Santa Ono and UM administrators are aggressively resisting any discipline from the conference on the matter, strongly encouraging Petitti to allow an NCAA investigation — in its third week — to be completed before penalties are administered.

In its letter, the university accepts full responsibility for the actions of the alleged orchestrator of the scheme, Connor Stalions, and believes that it was a one-man effort. The school says that there is no evidence that other coaches, most notably Harbaugh, knew of the wide-ranging system in which Stalions or associates attended games of Michigan opponents to record the opposing sidelines in an effort to steal play-call signals.

In a separate eight-page letter to the Big Ten, Harbaugh’s attorney, Tom Mars, mirrors many of the same arguments but also offers the first explanation for some of the questions that have dogged the Michigan coach since the Stalions scandal first broke. NCAA rules prohibit public comment during an ongoing investigation, effectively preventing the accused from publicly defending themselves.

Mars, for example, addresses the accusation that even if there is no proof Harbaugh did know about how Stalions was able to steal opponent’s signs, Harbaugh should have known, or at least should have been more curious, because Stalions’ was able to do it. It is legal to steal signs. It is the in-person scouting ring Stalions allegedly ran that is against NCAA rules.

However, Mars argues that since Michigan offered proof that both Ohio State and Rutgers had accurately stolen its play signals last season — presumably via game film, which is allowed — that figuring out the signs is not particularly difficult.

“When other teams had been legally acquiring Michigan’s signals with 100 percent accuracy for at least two years by studying Michigan game films, there was no reason for Coach Harbaugh or anyone else to believe that (Stalions) had not acquired his information about other team’s signals by using the same methodology," Mars wrote.

Michigan refers to Stalions as a “junior analyst” and says there is no evidence that his sign-decoding skills had any “material effect” on Michigan’s games. The letter cites Michigan’s average margin of victory (34 points) and the team won games by 49 and 28 points “without Stalions on the sideline." He was suspended three weeks ago and resigned last week.

Within its letter, Michigan lays the groundwork for arguments in potential legal action against the Big Ten if Harbaugh is suspended.

According to the letter, Petitti plans to use two avenues to levy penalties against the school:

(1) The Big Ten sportsmanship policy, and (2) the NCAA’s head-coach responsibility bylaw. The school pushes back on either notion.

Michigan claims the league is not following proper due process spelled out in the conference handbook — including an appeals process and a committee vote — and is instead “bootstrapping unproven rules violations through the sportsmanship policy,” the letter notes. Michigan says that any action from the league is a “breach" of the Big Ten handbook and any discipline against Harbaugh “would exceed the commissioner’s authority under the Sportsmanship Policy.”

Michigan claims the sportsmanship policy should not be used for this case and has not been used for such cases in the past, creating what the school describes as an “indefensible precedent.” The policy is most often used to address disparaging comments about officiating, post-game insults, profane language, obscene gestures, media posts and racial slurs.

“We are not aware of a single instance in which the sportsmanship policy has ever been deployed as a backdoor way of holding an institution or individual responsible for a rules violation,” the letter notes.

Also, the school notes, “nothing in your email suggests there is any basis to conclude that Coach Harbaugh committed an offensive action.”

Michigan pushes back on the Big Ten’s plan to punish Harbaugh under the NCAA’s head coach responsibility bylaw, as well. That is the "incorrect" use of the bylaw. The league rules don’t cite head-coach responsibility and there is no precedent to apply the sportsmanship policy to a head coach.

The university expresses “concern” that the Big Ten’s “rush” to punishment is “more about reacting to pressure from the public and other conference members rather than a desire to fairly and impartially apply the rules,” the letter states.

The school believes any punishment or judgment is premature. For instance, the letter says, no coaching staff members have been interviewed. “There is no reason to shortcut a full investigation in favor of summary punishment.”

The university says it has not seen any video evidence on which Petitti is basing allegations around and it questions four pieces of evidence that the league sent the school over the weekend. The four pieces of evidence include:

- records of Stalions’ tickets purchased and transfers,

- one unsolicited tip by an unidentified person claiming to have witnessed a person in Stalions' seat filming the sideline,

- a link to a public article that includes a “now-deleted” video of Stalions on the sideline of a Michigan game,

- a short video titled “UMass vs. PSU video” that “does not clearly show anything at all,” the letter says.

“From what we can tell, your email largely relies on rumor,” the letter says.

If Stalions’ associates were involved, the school casts doubt that any rule was violated. The NCAA’s in-person scouting policy is for a team’s “athletics personnel.” Also, Michigan claims that Stalions and associates recording games may not fall under the NCAA’s prohibition on recording because that applies to “field equipment deployed during games in which that institution participates.”

Meanwhile Mars cites the lack of authority under Big Ten rules for Petitti to usurp NCAA statutes to punish, warns that any penalty could be “an unlawful interference with [Harbaugh’s] employment” and cautioned that no decision should be made just to placate rival coaches who have reason to hope for Harbaugh’s demise.

“It should be self-evident that the Commissioner’s duty is to make sound decisions based on his own principles and those of the Conference and to disregard anyone’s desire for a rush to judgment — especially when they’re motivated by a desire to diminish Michigan’s opportunity to win the Conference and advance to the playoffs,” Mars wrote.

The Big Ten is expected to make a decision before the week’s end.