Student contracts cover issues such as discipline and bursaries
University students are facing "legalistic" contracts when they begin their studies - which can include requirements on dress and behaviour.
Teenagers do not realise what is in these lengthy documents, says the adjudicator of student complaints.
These contracts could be one-sided and non-negotiable, warns the adjudicator.
Vice-chancellors' body Universities UK said such "charters" helped to clarify the increasingly complex relationships between students and universities.
Baroness Ruth Deech, the independent adjudicator for higher education - who resolves complaints between students and universities - said the use of formal contracts and "charters" was likely to grow.
She said: "Our view on balance is that the student contract is not a good thing.
"It is useful to let students know that they have to work hard but I think the contract is too legalistic."
The contracts covered issues such as student accommodation, bursaries, discipline policies and the use of computers.
"I have seen one that even laid down that students should dress neatly when going to lectures. I don't know that that is enforceable," Baroness Deech added.
Concerns over the contracts were aired in the adjudicator's annual report.
It said: "Our concern with the new written university-student contracts is that students do not appear to favour them, regarding them as one-sided and non-negotiable, laying down, they would say, duties on students and using exclusion clauses to protect the university from liability."
President of Universities UK Professor Rick Trainor said there had always been some form of contract between the student and university.
"Universities are aware that the student-institution relationship is increasingly complex, with a variety of regulations and procedures already in place.
"As such, some institutions have found that student agreements, charters or guides developed with students are helping to clarify rights and responsibilities on both sides."
He said only one in five told a recent survey they had a formalised contract in place or were currently developing one.
"We also found the sector as a whole was cautious about the use of formal legal documents and their potential difficulties," he added.