Environmental cases

In the 2017 case of Merriman v. Friends of the Irish Environment, Barrett held that an unenumerated right to the environment exists in the Irish constitution, arising out of a case regarding extending planning permission for a runway at Dublin Airport.^[20] The case has not been overruled. However, the now-retired Chief Justice Frank Clarke did note in a 2020 Supreme Court decision that such a right had not yet been established by the Supreme Court and argued it was of a "very vague nature".^[21][22] The conservative approach taken by the Clarke Supreme Court contrasted markedly with the approach adopted by courts in many other jurisdictions, however, including the German Federal Constitutional Court, which has held national climate targets and permitted emissions to have violated fundamental rights.^[23]

Migration cases

In A v. Minister for Justice and Equality (2019), Barrett set aside a decision of the Minister for Justice and Equality which refused an application for family reunification, on the basis that a section of the International Protection Act 2015 was unconstitutional. Section 56(9)(a) did not recognise marriages of refugees for family reunification purposes which took place after arriving in Ireland.^[24] Although the case was concerned with a heterosexual marriage, it also impacted positively on LGBT+ couples who may not have been in a position to marry in countries of initial origin where same-sex marriage is not legal.^[25]

Jones v Minister for Justice and Equality (2019) was the subject of some political focus.^[26][27] Barrett refused to hold the Minister had been wrong in law to refuse the application for naturalisation of an Australian citizen who had been outside Ireland for 100 days prior to his application. The ruling held that the requirement in the Irish Nationality and Citizenship Act 1956 for one year's continuous residence for the period prior to an application must be given a literal reading, and concluded that there was no basis for the Department of Justice and Equality's discretionary policy of permitting six weeks absence from Ireland.^[28]

The implied effect of the judgment anyone seeking Irish citizenship would become ineligible if they broke the chain of one year's continuous residence.^[27] Researcher Conor O’Neill observed^[29] however that exactly this approach had been intended by the Government of the 15th Dáil. Barrett expressly anticipated in his judgment that it was for the Oireachtas to amend the legislation.^[26] The Court of Appeal subsequently dismissed an appeal from Barrett's ruling, noting that the trial judge had correctly concluded that the Minister's ‘finding’ was neither materially wrong nor irrational.^[30] but also held by majority that the lower court ruling on the construction of the legislation requiring unbroken residence in Ireland had been "overly literal", and set the ruling aside in that one respect.^[31][32] Because of the latter finding, any need for legislation (which the Minister had indicated would, if needed, be adopted "as an urgent priority") did not arise.^[33]

Heritage-related cases

In a 2016 case involving the relatives of the Easter Rising, he declared that Moore Street was a National Monument in 2016 in a 399-page judgment.^[34] Though welcomed by campaigners and some politicians, the decision was overturned by the Court of Appeal in 2018.^[35] Fully four years after this ruling, Barrett wrote a letter to the editor of The Irish Times expressing his disappointment of what he felt was a lack of vision by the authorities for Moore Street.^[36] The since-retired President of the High Court Peter Kelly was privately critical of this.^[37][38]