If you've been invited to an invite-only list, you have the option to leave it any time. To do so, open the list you want to leave, click
v beside the list name, and select "Leave List" from the menu that appears.
You can also leave a list from the sidebar by clicking the smaller
v icon that appears as you hover your mouse over any list.
If you are assigned tasks in the list, you will be prompted to reassign them to another teammate who is still a list member. Just select their name from the menu provided to continue to the last step.
To finalize this decision, click "Leave this list."
Once you've left a list, the only way to regain access to it is to be re-invited by another list member with access.