Re: This is the way it should work...
There's a fair amount of confusion about this. The 2400* number comes from Rees Mogg, who published a list of 2400 pieces of retained EU legislation and suggested that the public might want to vote on what we keep. It's here
From the site: "Retained EU Law (REUL), is a category of domestic law created at the end of the transition period. It is made up of certain pieces of EU legislation that were ‘cut and pasted’ onto the UK statute book as the UK’s own version of these laws. REUL is also made up of certain domestic laws that implemented EU law and were preserved as REUL on the UK statute book."
So those are the laws the bill is about when it references REUL.
The bill says
16 This Bill facilitates planned reforms to over 2,400 pieces of REUL. To ensure REUL comes to an end in the near future, a sunset of REUL by the end of 2023 has been included in the Bill.
17 The sunset will accelerate reform and planning for future regulatory changes, benefiting both UK business and consumers sooner.
18 The sunset will also increase business certainty by setting the date by which a new domestic statute book, tailored to the UK’s needs and regulatory regimes will come into effect.
19 A power to provide for an extension to the sunset has been included in the Bill, ensuring the efficiency of the REUL revocation process should a lack of parliamentary time, or external factors, hinder progress towards reform of retained EU law prior to the 2023 sunset date.
So, if the bill passes, and the government were to do nothing, all the those 2400* pieces of REUL will lapse at the end of 2023 unless they invoke clause 19 and extend the sunset date. That's the "bonfire" that many people refer to. I don't think it's helpful language and I don't think that UK gov has ever phrased it like that, but even the FT jumped on the bandwagon with "The UK government has invited people to use a new website to identify EU laws they wish to scrap, in a move that would deliver a “crucial boost to productivity”. Much as I don't like him, I can't find any direct quotes from Rees-Mogg about scrapping EU laws and not replacing them (5 minute web search, so I didn't look very hard).
Of course, no one's suggesting that the government will do nothing before the end of 2023, but there's a view that there aren't enough civil servants working on this in order to review and replace all the REUL - the Grauniad article below has a couple of quotes to this effect. The government could just assimilate a lot of the REUL or extend the sunset date - the bill allows for that both of these. Note also that the Brexit treaty limits what we can do in some areas, like employment law, to prevent the UK reducing regulations which would allow us to compete on "unfair" terms with Europe.
My view, for what it's worth, is that it's a bad and pointless bill overall. There's a need, as Peter2's first post highlights, to separate UK law from the EU court and case law, but the rest of the bill is pointless; REUL legislation could stay on the books to be dealt with in some sort of priority order and that priority shouldn't be based on whether or not it came about because of our membership of the EU. If we're going to change employment law then the EU-derived elements are less important than zero hours, employee definitions, IR35, etc. in my opinion (other opinions are available).
* they've just found another 1400 laws that will also need to be covered by this bill. See