[antientropic]

No, the UK cannot unilaterally withdraw before the end of the two year period. An earlier withdrawal is only possible if the UK and the EU both agree.

[gpderetta]

well, technically as long as it is aiming for an hard brexit it can withdraw unilateral whenever it wants. The two year period is a safety blanket to negotiate a better deal while still enjoying the existing rules.

[pmyteh]

According to the text of Article 50, a withdrawing state remains bound by the Treaties (and thus by EU law) until either (1) an exit agreement is made and enters into force; or (2) two years pass after Article 50 is invoked.

So the UK can't 'withdraw unilateral whenever it wants' without creating a giant legal problem as its erstwhile partners attempt to enforce its (still extant) obligations.

[gpderetta]

the UK is sovereign, so it certainly can. The other parties can of course impose sanctions (likely) or go to war (unlikely, hopefully).

[antientropic]

Sure, if the UK is willing to violate its treaty obligations, it can do whatever it wants. But the context of the discussion was the legal situation under Article 50.