No, you cannot reuse or edit a previous Campaign that either you (as an admin) or a previous admin has 'ended'. The purpose of ending a 'live' Campaign is so that the content is not recirculated amongst your employees; this can be for a number of reasons deemed appropriate by the admin at the time of ending the Campaign.

This is also reflected in the Reporting per course/phish. 

• You can, however, copy the relevant Fusion template and rename it, and then either update/recirculate it as part of a new Campaign.
• Likewise, you can also copy a phish template from its archive state and rename it, again either to update/recirculate it as part of a new Campaign.