You can delete only those match lists that are not used in any content filtering or file filtering rules or any content filtering policy templates.
To delete a match list
In the console on the primary navigation bar, click Policies.
In the sidebar under Content Enforcement, click Match Lists.
In the content area, under Match Lists, select the match list that you want to delete.
In the sidebar under Tasks, click Delete match list.
In the confirmation dialog box, click OK.
On the toolbar, click Deploy changes to apply your changes.