Thread by @Brigid_Fowler

OK, I've caught up with Twitter again & there's both some v. interesting exchanges & still a fair bit of apparent wider public confusion re: the date UK leaves the EU, A50 #extension & the SI to change 'exit day'. So, in interests of end-of-the-week clarity, here's another go. 1/

The date UK leaves the EU is an intl matter. It's not determined by whatever UK domestic law may say.Changing 'exit day' in UK law doesn't change date UK leaves the EU. See posts this wk by @woodstockjag & @DomWalsh13 as well as me, & eg @ProfMarkElliott & @carlgardner on here 2/

UK & EU have now agreed that A50 period, at the end of which the departing state leaves the EU, will be later than 29/3. The only way the UK still leaves the EU on 29/3 is if UK gov, or EU, or both, renege on the agreement reached last night. 3/

Last night's agreement has been formally accepted in writing by UK & is now a formal European Council Decision published today in EU Official Journal. 4/
eur-lex.europa.eu/legal-content/…

UK needs to amend the 'exit day' that's in the EU(W)A (ie 29/3) *not* to affect the date on which it leaves the EU but in order to bring its domestic law into sync with it. If the two dates get out of sync, UK will have a legal mess (technical terminology klaxon). 5/

EU(W)A says 'exit day' may be amended by Statutory Instrument (SI). By law, under the EU(W)A, the relevant SI must be subject to the draft affirmative procedure ie it must be approved by both Houses. SIs can only be laid before Parliament by a minister. SIs are not amendable. 6/

re: idea of changing 'exit day' by primary legislation rather than SI, I can't see this would be needed (given SI could be done quickly), legally unproblematic (given EU(W)A expressly provides for changing 'exit day' by SI) or politically wise (given primary leg is amendable) 7/

Passing legislation to change 'exit day' in EU(W)A as a technical matter to match intl state-of-affairs is separate Q from Q (which some constitutional lawyers are debating) of if/how gov ought to seek/have sought parly authorisation/approval for agreeing the A50 extension. 8/

re: speed/timing of 'exit day' SI process, my post at start of this wk was prob not as clear on this as it sld have been. There's not an absolute deadline (Monday or otherwise) by which the SI needs to be laid before Parl for it to be approved by 29/3. 9/
hansardsociety.org.uk/blog/changing-…

Obviously, the later next week it gets, the tighter it'll be, but process fixes are available & it could be done quickly if nec. We're looking some more into the exact choreography, so look out for possible new content from us @hansardsociety early next week. 10/

re: when SI can/will be laid, gov saying will only lay it after planned #meaningfulvote3 next wk. I find it hard to see, politically & technically, how gov can lay it til we know new default Brexit date ie til we know whether HoC is approving #WithdrawalAgreement next wk /ends