Afaik, it's not only a free re-assign, it's actually a ful unassign from both, home and guest campaign, for all chars. This is done to a) reset the leaderboards and b) give players free choice of options considering the scoring changes.The option to unassign yourself from campaigns is being investigated for the future, and every character will get a free reassign when Imperial City is released, so discuss with your friends which of the different rulesets you would like to play with your main PvP characters and go from there
With the upcoming change to being able to "jump" into Cyrodiil from friends list or guild list, what do you plan on doing for those of us with multiple characters v14-16 spread evenly across the 3 factions? You are severely limiting our options. For example I cannot test anything on PTS non AD because my Sorc is AD and on the only campaign available. My friends and I have ran into this option quite a bit while leveling new characters on new factions on Live already pre-patch. Without the ability to "jump" you just locked out quite a few people.
The option to unassign yourself from campaigns is being investigated for the future, and every character will get a free reassign when Imperial City is released, so discuss with your friends which of the different rulesets you would like to play with your main PvP characters and go from there