The Isle of Man is a separate jurisdiction to the United Kingdom and as a result has its own legal system. The principles of the Manx legal system are based on English common law and the Island follows very closely the precedents set by the English Courts if there is no conclusive Manx precedent already established.
As far as the McKenzie Friend Organisation is aware there are no active McKenzie Friends operating on the Isle of Man.
The Island is a self-governing British Crown Dependency - as are Jersey and Guernsey in the Channel Islands - with its own parliament, government and laws. The UK government, on behalf of the Crown, is ultimately responsible for its international relations. The Queen, who is ‘Lord of Mann’, is the Manx Head of State and is represented on the Island by the Lieutenant Governor.
Isle of Man - Constitution
The Isle of Man is not, and never has been, part of the United Kingdom, nor is it part of the European Union. It is not represented at Westminster or in Brussels.
However, given the Manx legal system is similar to, but not the same, as the legal system in England and Wales McKenzie Friends are allowed and they do have their own Isle of Man ‘Self Representation’ guidelines with ‘McKenzie Friend’ guidelines included as Annex 4 - a copy of which can be found here.
The Isle of Man sometimes referred to simply as Mann is a self-governing British Crown dependency in the Irish Sea between Great Britain and Ireland.