Over a thousand barristers have signed a letter to be sent to the Prime Minister stating that the referendum is not legally binding and that primary legislation would be required before Article 50 can be invoked.

This mirrors other interpretations I have seen, that the referendum of itself is not enough to invoke Article 50. That other steps would be required. These range from a debate and vote in Parliment, up to a requirement for new legislation.

The letter states:

The referendum did not set a threshold necessary to leave the EU, commonly adopted in polls of national importance, eg, 60% of those voting or 40% of the electorate. This is presumably because the result was only advisory.

The outcome of the exit process will affect a generation of people who were not old enough to vote in the referendum. The positions of Scotland, Northern Ireland and Gibraltar require special consideration, since their populations did not vote to leave the EU.

The parliamentary vote should take place with a greater understanding as to the economic consequences of Brexit, as businesses and investors in the UK start to react to the outcome of the referendum.

For all of these reasons, it is proposed that the government establishes, as a matter of urgency, a royal commission or an equivalent independent body to receive evidence and report, within a short, fixed timescale, on the benefits, costs and risks of triggering article 50 to the UK as a whole, and to all of its constituent populations. The parliamentary vote should not take place until the commission has reported.

Yahoo News: Brexit: Over 1,000 barristers sign letter saying EU referendum vote is not legally binding

The Guardian: Parliament should make final decision on whether to leave EU, barristers say