Simon Coveney (Cork South Central, Fine Gael) | Oireachtas source

The legislation that is passed in the UK is a matter for the British Government and Prime Minister. He now has a strong majority and can legislate for what he sees appropriate. Since he has a strong majority, he can also amend that legislation in the future if he wants to. UK and British legislation is a matter for Britain. The EU will not be bound by British law and will negotiate on the basis of content and trying to get the best possible deal for the EU, while also respecting the British mandate in those negotiations. There has been a lot of talk about legislating in a way that prevents the British Government from seeking a further extension beyond next year. That is a political decision for the British Prime Minister. Whether legislation is in place is largely incidental in my view because his decision can be facilitated by changing such legislation in the future if he wants to do so because he has a majority.

See this speech in context