Jonathan Rickford advocates taking the common sense approach towards Art 50 & the role of Parliament
Triggering Art 50 of the EU treaty will most probably lead to UK exit from the EU within a period of two years after notice of the decision to withdraw is given (the period can be extended if all 27 remaining members states agree, but that seems unlikely). Exit will come about either in accordance with an agreement between the UK, the Council of Ministers of the 27 member states and the European Parliament concluded within that period, or by the failure of the negotiations to conclude in time.
Whether the government has authority under the Royal Prerogative to give notice is a legal question decided in the negative by the Divisional Court on 3 November, but to be finally resolved by the Supreme Court before the year end (see Michael Zander QC, "Art 50: the verdict"). If the Supreme Court follows the reasoning of the High Court—that notice changes UK law—then primary legislation is required to