Essentially Labour wants to reestablish an alternative law making power base to rely upon when it doesn't hold the keys to No. 10. That's what the EU is about for them
Labour was and still is genuinely divided on Brexit. As were/are many actual and potential Labour voters.
However, establishing an alternative power base to No 10 to protect employment, consumer, citizen, and environmental rights etc was exactly what the EU was about for me.
All my fears and more coming to fruition now showing I was right to want Brussels as a counterweight to the vested self interest of Tories in power.
www.theguardian.com/technology/2022/jun/17/uk-plan-to-scrap-cookie-consent-boxes-will-make-it-easier-to-spy-on-web-users