Re: I hate to be pedantic but...
The UK protects its own murderers, ie the paratroopers from Bloody Sunday among others such as the many loyalist terrorists who were on the payroll of various UK and local NI government branches (RUC, UDR, MI5 etc). Investigations into those crimes have been consistently obstructed (especially by "disappeared" records) or hampered by inadequate resourcing, and now may be outlawed entirely by Westminster.
The ROI government is not, and has never been, synonymous with the IRA.
Further, the border between the ROI and NI is now the only major land border between the UK and the EU and is of great importance not just to the Republic but to the Single Market
https://www.bbc.com/news/uk-32887445
https://cain.ulster.ac.uk/issues/collusion/stevens3/stevens3summary.pdf
https://www.theguardian.com/uk/2001/feb/26/northernireland.ireland
https://commonslibrary.parliament.uk/research-briefings/cbp-8352/
https://hudoc.echr.coe.int/app/conversion/docx/?library=ECHR&id=001-70236&filename=O%60LOUGHLIN%20AND%20OTHERS%20v.%20THE%20UNITED%20KINGDOM.docx&logEvent=False