Citizens of other EU countries cannot be deported simply on the grounds that they have committed criminal offences. The person’s behaviour must be a “genuine, present and sufficiently serious threat affecting one of the fundamental interests of society”. An offence attracting a prison term of just four months is unlikely to be considered serious enough and the general rule is that a custodial term of at least 12 months must be imposed before the individual is even considered for deportation.
Mr Cameron tried, in his famous deal to encourage us to remain in a “reformed” EU, to tinker with the words of the legislation. His deal proposed a change which would allow host countries to keep out or deport people whose behaviour is “likely" (as opposed to “does”) to represent a genuine and serious threat to public policy or security”. It sought to take the emphasis away from present conduct by individuals to look much more closely at their past. However, all that, of course, is history.
At last autumn’s Conservative Party conference Home Secretary Amber Rudd suggested that the UK need not wait for Brexit to change the rules:
"We are going to overhaul our legislation to toughen our approach to deporting EU criminals and those who abuse our laws. We will make clear what our courts must take into account when considering the deportation of EU criminals, aligning their fortunes more closely with those from outside the EU.” It’s not quite clear whether this change will be made before Brexit as I have seen no sign of it yet.
Yet another good reason to be thankful that the Leavers prevailed in June. Imagine any “normal” country being told “Dreadfully sorry you have barrow loads of foreign criminals in your midst. Unfortunately, under the rules, you’re stuck with them.”
Having said that, I’m not that confident that the situation will improve. There are thousands of non-EU foreign criminals in the UK “awaiting deportation” who have no protection under EU rules but I don’t see them being deported in any vast numbers. Mind you, it seems they've made a start with one of those posing the most serious threat to the peace and stability of the UK:
https://www.theonlinecitizen.com/2017/02/27/singaporean-wife-of-british-man-allegedly-deported-by-uk-govt-to-prevent-legal-action/