On Monday, Trenton Oldfield won his appeal against Theresa May's decision to deport him to Australia after he carried out a direct action protest against elitism at the Oxford Cambridge boat race in 2012. The home secretary had deemed Oldfield's presence in the UK to be "undesirable" and "not conducive to the public good" after he was convicted of causing a public nuisance when he swam into the Thames and disrupted the boat race last year. Oldfield's win is not only a victory for the right to protest, but a serious defeat for May's deportation policy.

May had delivered a tub-thumping speech to Tory party members at their September conference in which she promised to "deport foreign criminals first, then hear their appeals". In spite of this, at yesterday's tribunal the Home Office's legal representative did not seem to be trying very hard to win the case. He asked few questions of Oldfield and his wife, Deepa Naik, and chose not to quiz the witnesses at all. He presented little evidence, basing his entire case on the fact that Oldfield had carried out a direct action protest. It seemed the Home Office expected to lose. Was this a U-turn in disguise?

May should never have taken the decision to deport Oldfield. In cases of foreigners who serve sentences of less than 12 months, the home secretary has the discretion to order deportation if she considers it to be "in the public interest". Oldfield's crime was to carry out a peaceful direct action protest in the name of equality. At his tribunal hearing, he spoke of how he had not expected to have been dealt with so harshly by the state. Britain, he believed, was a "mature democracy", which this year commemorated 100 years since Emily Davison staged her final protest calling for women's suffrage at the Epsom Derby, where she was trampled by King George V's horse. But the historical tradition that May seems to be following is a quite different one: Britain's shameful history of deporting political activists to Australia – the Tolpuddle Martyrs in 1834, the Chartists in 1842 and the Fenians in 1868, to name but a few.

The state's reaction to Oldfield's protest is one of a long list of the coalition government's repressive responses to dissent. Recall the police brutality and criminalisation with which students were met when they resisted the tripling of student fees three years ago; scenes which were replayed on campuses last week when students staged "cops off campus" protests following the violent eviction of a student occupation calling for an end to the marketisation of education.

Oldfield and his wife have lived through months of anxiety, facing the possibility that their family, including their five-month-old daughter, could be separated from each other. This anguish is felt by thousands of migrants forcibly removed from Britain every year. Addressing the press following his victory, Oldfield called for attention to be focused on all the other migrants "going through the same process". Most deportees do not have the cultural capital and support network from which he, as a white middle class man, has benefitted.

Consider the case of Luqman Onikosi, an anti-racist activist who suffers from hepatitis B and is under threat of deportation to Nigeria, where he will be unable to access treatment. Or Isa Muaza, for whom May ordered an "end of life" plan be drawn up after he went on hunger strike for 100 days in protest at his deportation to Nigeria. Despite being so ill that he had to be carried out of Harmondsworth immigration removal centre in order to be deported, May refused to back down. As a result of his protest, Muaza's case has attracted the support of MPs, the public and celebrities. The home secretary no doubt fears that other migrants in seemingly powerless positions will be similarly inspired to resist deportation through protest.

In carrying out his protest against elitism, Oldfield focused on a symbolic site: the Oxford-Cambridge boat race. In winning his appeal, he succeeded in disrupting something weightier and more sinister: the attempt by May – herself an Oxford alumnus – to use his case to send a message of deterrence to migrants who might consider engaging in political protest.