A ruling by the Irish Supreme Court on climate change policy could have "huge ramifications" across Europe, the group which took the case has said.
On Friday the Supreme Court quashed the government's 2017 National Mitigation Plan.
Judges ruled that it did not give enough detail on the reduction of greenhouse gases.
The case was brought by the environmental group Friends of the Irish Environment.
The Irish government welcomed the ruling and said it would "carefully examine the decision".
Friends of the Irish Environment spokeswoman Clodagh Daly told BBC News NI the verdict was "crystal clear" and would have implications across Europe.
She said: "It shows governments have to do more to protect their citizens from the worst impact of the climate crisis.
"We know that the transition to the low-carbon economy is technologically feasible - there is no legal basis for a lack of political will.
"Governments around the EU have no excuse now."
She said she hoped it would put pressure on the Northern Ireland Executive to follow a similar approach.
Ms Daly added that while "climate change knows no borders" and emissions were counted on an all-island basis, she noted "how we respond to the climate crisis is separate".
She said it meant the Republic of Ireland's government could "no longer make promises it will not fulfil" and had a legal obligation to protect citizens from the worst impact of climate change.
'No climate act'
James Orr, the Northern Ireland director of Friends of the Earth, said the decision was a "wake-up call for politicians to take effective climate action both here and across the world".
"Not only do we have a moral duty to stop the climate crisis but we now have a legal duty as well," he said.
"The argument for decisive climate action has become a lot stronger as a result of this epic court case."
What was the case about?
Bringing the case, Friends of the Irish Environment argued the Irish government had a responsibility to reduce greenhouse gas emissions within the next couple of years or face the serious impacts of climate change.
It contended the increase in greenhouse gas emissions allowed in the 2017 National Mitigation Plan was contrary to the 2015 Climate Action and Low Carbon Development Act.
These pieces of legislation make it a requirement to have a published plan for transitioning to a low carbon climate resilient and environmentally stable economy by 2050.
The unanimous judgment of the Supreme Court ruled that more specificity was needed about how objectives laid out in the 2015 legislation were going to be met by 2050.
This was decided on the grounds that a reasonable and interested person could make a judgement both as to whether the plan in question was realistic and as to whether they agree with the policy options.
It was ruled that this standard for specificity was currently not met.
Climate Action Minister and Green Party leader Eamon Ryan said in a statement: "I welcome the judgement of the court and congratulate Friends of the Irish Environment for taking this important case.
"We must use this judgement to raise ambition, empower action and ensure that our shared future delivers a better quality of life for all."
The statement said the new government was "now committed to an average 7% per annum reduction in overall greenhouse gas emissions from 2021 to 2030, equivalent to a 51% reduction over the decade and to achieving net zero emissions by 2050".
The department will now "carefully examine the decision and consider its implications".