Now that the UK Parliament has again rejected the Withdrawal Agreement and reiterated its desire to not leave without a deal, the UK may choose to apply for an extension to Article 50. Such an extension must be approved by the EU and all its member states. If this approval process is still ongoing by the original Brexit date, can the extension take effect while the approval process is still ongoing?
Section 3 of article 50 of the Treaty on European Union states that:
The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.
In other words, there is no extension unless and until the European Council agree to it before the deadline.
1Furthermore, if this odd scenario were to take place where the EU was debating an extension past the point where the UK left the EU, then the debate would be over as the UK would no longer be a member requiring an extension anyway. I'm fairly certain (though not entirely) that the matter will be more cut-and-dried than that.– ouflakMar 14, 2019 at 17:07