Cases of suspected financial fraud and 'tug-of-love' child abduction cases with a UK dimension are among those set to be affected in the event of a no-deal Brexit.
The warning, from a leading Irish solicitor, came as a European Commission notice signalled a no-deal Brexit has the potential to have a significant impact on cross-border commercial and civil litigation in the EU.
This is because the UK's participation in European regulations governing jurisdiction and enforcement of judgments in civil and commercial matters will cease.
EU instruments facilitating cross-border co-operation on various issues, including the service of proceedings and the taking of evidence, are also scheduled to fall away.
Seán Barton, a partner in one of Ireland's largest law firms, McCann FitzGerald, said he could foresee problems in certain types of cases where international co-operation is essential.
One example is in the area of fraud, where under EU arrangements any member state can issue a freezing order over a bank account where there is a claim of fraud in another member state.
"If someone in the UK has defrauded me out of €500,000 and the money is sitting in a bank account in Dublin, as of right now I can issue my claim in the UK courts and the High Court in Dublin can assist, under cross-border co-operation, and give me an injunction freezing that bank account," he said.
"But if there is a hard Brexit, after April 1 the Irish court couldn't give an injunction in those circumstances because there is no legal basis for it to do that."
Similarly, he sees issues arising in child abduction cases where there is a split between the parents and one of them takes the child to the UK.
Mr Barton said there was an established EU regime in place to determine which country's courts would get to decide on the outcome of such matters.
"If any EU country pulls out, that creates an uncertainty as to whether they are going to apply exactly the same rules, because they are no longer obliged to," he said.
Another issue of concern is the recognition of judgments issued prior to the March 29 withdrawal date.
The UK has indicated it will continue to enforce judgments given in other EU member states where the proceedings were initiated before Brexit.
However, the situation is not as straightforward when it comes to UK judgments being recognised in the EU.
According to the European Commission notice, unless a UK court judgment has gone through a recognition process known as exequatur before the withdrawal date, EU rules on recognition and enforcement will not apply.
This will be the case even where the judgment was handed down before the withdrawal date or enforcement proceedings were commended before the withdrawal date.
Mr Barton said the uncertainty could be alleviated for now through a withdrawal agreement.
"If that doesn't happen, courts can only act on the basis of statutory powers given to them. They can't pluck an ability to recognise a foreign judgment, or to help a foreign court, out of thin air," he said.