Why is the backstop so controversial? The measure hampered Brexit negotiations and was one of the main reasons why the negotiated divorce deal was rejected by the British Parliament. On 15 January 2019, the UK Parliament rejected a government request for approval of the draft Withdrawal Agreement. In late January 2019, many Conservative and DUP MPs backing Brexit continued to reject a backstop with no specific end date, fearing it would tie the UK to many EU rules indefinitely.  In the votes that followed, most conservative rebels voted in favor of the Withdrawal Agreement and the backstop, although the DUP continued to oppose it, contributing to its continued defeat. Indeed, without a trade agreement, trade relations on goods between the United Kingdom and the EU (including the Republic) would revert to the conditions of accession to the World Trade Organisation (WTO). These stipulate that the same tariffs and controls must be applied without distinction between all WTO Members (most-favoured-nation test), unless some Members have concluded a trade agreement.  This principle would also apply to cross-border trade in Ireland in the absence of a trade agreement. EU officials insist they will not reopen the withdrawal agreement reached with Theresa May last year – of which the backstop is an integral part. The backstop would have required Northern Ireland to be maintained in certain aspects of the single market until an alternative agreement between the EU and the UK is reached.