Upvote:3
If I follow you correctly, you entered the EU with two litres of spirits. Enforcement might be complicated by your complex bag checking wizardry but your legal position seems clear to me: You have crossed an external border once, there is no reason for any limit to be βresetβ. Even if you only have to clear customs with your second bag on your final destination and nobody will search it in London, you are not in transit to anywhere outside the union and that's when you violated the rules.
More interesting, you could in theory buy everything you want in London and then show up in Paris with a lot more alcohol than you had the right to import from the US. You better keep all the receipts in case your luggage gets searched!
And for even more arcane ways to fraud: Leave the extra bottle with a friend in Paris or send it by post to yourself! But you would in any case have entered the EU with more spirits than allowed without paying duty, there is no doubt about that in my mindβ¦