[pknight]

You're not actually addressing the myriad of cases in which the principle of unilateral revocation is warranted. You're merely asserting that it's improbable that member states would negotiate in bad faith or vote in a hostile manner contrary to the leaving member's interests.

A50 was not just constituted to protect the remaining members when a member departs, it was to show members that leaving is possible. If the leaving member has no power in this process and with bilateral revocation the UK in this case has very little leverage, it precisely sets up the circumstances in which any number of member states can muck up the process in a way that harms the welfare of the leaving country. That can't be right.

Unilateral revocation in the only way it is possible keeps the EU27 honest if it were intent on not being reasonable. Mind you there are plenty of people in the UK who feel the EU is not negotiating in good faith as it stands. Unilateral revocation certainly diminishes their leverage and it is undesirable to have to deal with it from the EU27's point of view, but this is a good thing. The EU27 should not have absolute power over a member who expressed a desire to leave.

The only scenario in which unilateral revocation encourages shenanigans is a hypothetical scenario that simply doesn't work. As I've explained in a previous comment, if the leaving member initiates revocation as a means of resetting the negotiation window or as a means of exacting new concessions, it will backfire, the benefits would be nullified and it would be a stupendously high risk to take. After all, if the UK negotiates in bad faith, the EU27 would contest it in the CJEU with the possibility of losing. It would be entirely unprepared to take the blow of a cliff edge Brexit and kill any chances of a favourable FTA from happening for years if not decades.

Note that in all cases bilateral revocation is preferable and probably is how things would go, but you don't need to stretch your imagination that far to imagine whether unilateral revocation should be a right when only one of the EU27 is needed to block bilateral revocation and send the UK into unmitigated chaos.

[Nursie]

I think we see this very differently, article 50 isn't, to my mind, an expression of a desire to leave, but the actual start of the process.

[pknight]

A50 is specifically worded as to notify an intent to leave. Intent can change, the A50 text sets nothing in stone other than the fact that barring any further intervention the exit date ends 2 years from the notification date. That's it.

I think you're discounting the fact that up to the departure date the UK is a full member with the ability to exercise its rights, including the right to change its mind, especially if the conditions merit it. We both agree that all parties must conduct the A50 process in good faith. You haven't convinced me why the option of unilateral revocation discourages good faith negotiation, or how it encourages bad faith negotiation.

Note that the legal arguments in favour of unilateral revocation specifically relate back to other EU laws, international law and the EU principle of closer union.