LONDON (AP) — Britain’s government on Monday proposed new legislation that would unilaterally change post-Brexit trade rules for Northern Ireland, despite opposition from some U.K. lawmakers and EU officials who say the move violates international law.

The proposed bill seeks to remove customs checks on some goods entering Northern Ireland from the rest of the U.K. That will override parts of the trade treaty that Prime Minister Boris Johnson signed with the European Union less than two years ago.

British Foreign Secretary Liz Truss maintained that Britain is acting within international law, and blamed the EU for blocking a negotiated settlement. The European Commission said it could take legal action against the U.K.

European Commission Vice President Maros Sefcovic said the EU’s executive arm will consider launching new infringement procedures to "protect the EU single market from the risks that the violation of the protocol creates for EU businesses and for the health and safety of EU citizens.”

In Ireland, Prime Minister Micheal Martin said it was “very regrettable for a country like the U.K. to renege on an international treaty."

Brushing aside criticism, Johnson told reporters that the proposed change is “relatively simple to do."

“Frankly, it’s a relatively trivial set of adjustments in the grand scheme of things," he told LBC Radio.

He argued that his government's “higher and prior legal commitment” is to the 1998 Good Friday agreement that brought peace and stability to Northern Ireland.

Arrangements for Northern Ireland — the only part of the U.K. that shares a land border with an EU nation — have proved the thorniest issue in Britain’s divorce from the bloc, which became final at the end of 2020. At the center of the dispute is the Northern Ireland Protocol, which now regulates trade ties between Northern Ireland, which is part of the U.K., and the Republic of Ireland, part of the EU.

Britain and the EU agreed in their Brexit deal that the Irish land border would be kept free of customs posts and other checks because an open border is a key pillar of the peace process that ended decades of violence in Northern Ireland.

Instead, to protect the EU’s single market, there are checks on some goods, such as meat and eggs, entering Northern Ireland from the rest of the U.K.

But the arrangement has proved politically damaging for Johnson because it treats Northern Ireland differently from the rest of the United Kingdom. Northern Ireland’s Democratic Unionist Party has refused to return to the region’s power-sharing government until the protocol is scrapped or substantially changed.

The bill to override that arrangement is expected to face opposition in Parliament, including from members of Johnson's own Conservative ranks. Critics say unilaterally changing the protocol would be illegal and would damage Britain’s standing with other countries because it's part of a treaty considered binding under international law.

In Brussels, Sefcovic said the protocol was the “one and only solution we could jointly find to protect the hard-earned gains of the peace process in Northern Ireland."

He added that the EU remains open to discussions with the British government to find a solution to the dispute.

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Associated Press reporter Samuel Petrequin in Brussels contributed to this story.

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Follow AP's coverage of Brexit at https://apnews.com/hub/brexit.

Sylvia Hui And Danica Kirka, The Associated Press