The warning from two experts on higher education law comes after the vice-chancellor of the University of Bedfordshire was finally confirmed as the next head of the Office for Fair Access, after almost a month of political infighting within the coalition.
Confirmation of his appointment came in a press release on 20 February accompanied by a letter from Vince Cable, the business secretary, explaining to a cross-party group of MPs why he had chosen to overrule their recommendation to reject Professor Ebdon. Mr Cable said the report from the Business, Innovation and Skills Committee - backed by just four out of 11 MPs, all Conservative - had produced no "new, relevant facts" to prevent Professor Ebdon's selection.
Mr Cable reiterated that the appointment was also approved by David Willetts, the Conservative universities and science minister.
Backbench Tory MPs - who are fuming that Mr Cable has forced through the appointment - did their best to stop the announcement passing quietly by calling on the business secretary to account for his actions in a House of Commons debate that laid bare the split in the coalition.
During the exchanges, Liberal Democrat MPs were visibly buoyant at what they regard as a key victory, while Conservative MPs struggled to contain their anger at an appointment they believe will lead to "social engineering".
However, David Palfreyman and Dennis Farrington, authors of The Law of Higher Education (the second edition of which is published next month), warned that politicians on all sides may have been overreacting, given the limited powers Professor Ebdon will enjoy.
Mr Palfreyman, director of the Oxford Centre for Higher Education Policy Studies, said the legislation underpinning Offa - brought in by the last Labour government - was clear that it could regulate universities' attempts to boost applications from poorer students, but not admissions. He also said that with any additional proposed powers for Offa now on hold due to the postponement of a new higher education bill, Professor Ebdon could face legal action if he tries to reprimand institutions for failing to meet any target on admissions.
"If the government really wants to be able to tell higher education institutions whom to admit, then it needs to grant itself appropriate draconian powers in new legislation. That is politically just not going to happen, no matter how guilty the Lib Dems feel about fees at £9,000."
Dr Farrington said that universities could legally face sanctions from Offa if they had "manifestly" failed to do what they had agreed to in access agreements on promoting applications, but there was a "clear distinction" with admissions.
"The principle of university autonomy...applies to the exercise of the power of selection and admission. That is a principle upheld internationally and...there is no way any government will attempt to give instructions about actual admissions," he said.
Mr Palfreyman said the real test would come if Professor Ebdon threatened to cap fees at a particular university over a failure to meet admissions targets. When he appeared before MPs on the BIS committee, Professor Ebdon said he could use the "nuclear option" of capping fees, although he did not specify the circumstances.
"The key issue is whether the Russell Group vice-chancellors roll over when Les declares he has weapons of mass destruction or whether the Russell gang reach for the lawyers and threaten judicial review," Mr Palfreyman said.
He added that in appointing Professor Ebdon, Mr Cable and Mr Willetts should have been made aware by government lawyers of the limitations he would face. That is likely to be a key reason why Mr Willetts approved the appointment in the face of backbench Tory opinion.