The High Court in Belfast will rule today on Northern Ireland's entitlement to veto the UK's departure from the European Union – the first opinion by a UK judge on Brexit. With other legal challenges under way in Britain, the outcome will be closely monitored by politicians and financial<br/>markets.<br/><br/>The campaigners argue Brexit cannot be imposed on Northern Ireland because the 1998 Good Friday Agreement, an international treaty involving the neighbouring Republic of Ireland, gives Northern Ireland residents control over future constitutional change. In the June 23 referendum on EU membership, Northern Ireland voted 56 per cent in favour of the UK staying in the bloc, while across the entire kingdom, 52 per cent voted to leave.