Meredith Wilkinson, writing in Times Higher Education suggests "Disabled students still need online learning options" (21 May 2022). They point out at least 17% of UK university students had a disability and online learning has advantages for many of these students, and suggest universities should not withdraw this option with the end of the COVID-19 pandemic. I would put the case more strongly than that. The UK, Australia, and many other countries have anti-discrimination legislation. Withdrawing online learning would discriminate against sections of the community, and may therefore be illegal.
Laws prohibits discrimination based on disability, gender, religion, race, and other grounds. Universities showed they can deliver online learning due to the COVID-19 pandemic (although some had been doing this for decades). That learning benefits students who have a disability, or can't get to campus due to work, family, community, and cultural commitments, or simply due to were they live. If online learning is withdrawn, those students will find study harder, or impossible. If online learning was very expensive, or technically difficult to provide, then universities would have a defense in law for not doing it, but it isn't expensive, or difficult, so they must do it?
In reality most students, at least in Australia, were studying mostly online before the pandemic. By 2019 universities had put in place learning management and video systems to supplement face to face teaching. These were the same systems needed for fully online learning (I was using them for teaching online at ANU from 2009). The removal of online learning options will not reduce costs, as the video and learning systems for it will still be in place to support courses officially classified as on campus. However, students will have their flexibility to study how they want, and need to, restricted, for no good reason.
This may seem absurd, but then so did the idea that services must be provided online. Surely a sporting organisation is not required by law to have a web site blind people can use? The answer is yes they are, as established in the human rights case "Maguire v Sydney Organising Committee for the Olympic Games" (2000), which I was an expert witness for. The Beijing Olympics later asked me to go over to help them not make the same mistake.