The EU?sent a letter of formal notice to the UK Thursday over a UK bill that breaches the EU-UK Withdrawal Agreement and thus violates international law.

Ursula Von der Leyen, the European Commission president, announced Thursday that it had launched a formal infringement procedure against the UK through a letter of formal notice sent to the UK for breaching its obligations under the Withdrawal Agreement by passing a bill known as the United Kingdom Internal Market Bill.

The bill, which was introduced in the House of Commons earlier this month, sets up rules for the operation of the UK internal market once the Brexit transition period ends. It contains certain?provisions that would allow UK ministers to override parts of The Withdrawal Agreement—particularly, the “Protocol on Ireland and Northern Ireland” section.

The Protocol on Ireland and Northern Ireland essentially requires that Northern Ireland continue to enforce the EU’s customs rules and rules on product standard so as to make checks on goods traveling from Northern Ireland (a non-EU country) into Ireland (an EU country) unnecessary.

However, the bill would—if passed into law—allow?UK ministers to “disapply” these rules and would thus hinder the implementation of the agreement.

The UK maintains that the contentious provisions are just a legal safety net to be used if negotiations with the EU on?how to implement the Protocol fail.?However, The EU, which had given the UK until the end of September to remove the contentious provisions from the draft bill, stated that the bill is a violation of the agreement and issued a letter of formal notice to the UK shortly after the bill received its final approval from members of the House of Commons on Tuesday.

“The draft bill is, by its very nature a breach of the obligation of good faith laid down in the withdrawal agreement. Moreover, if adopted as is, it will be in full contradiction to the protocol on Ireland and Northern Ireland,”?said Von der Leyen.

The bill cleared the House of Commons?with a 340-256 vote in favor of passing the bill. It will now move to the House of Lords for debate.