I made a little mistake; after creating my league I invited some friends and after one signed in I tried to click on his team trying to see details about it if possible, only to kick him from my league because I didn't notice the "kick" link that appeared by hovering over a team.

Can he rejoin my league without spending an extra ticket or did he lose it and needs a new one to enter?

The suggestion is of course about this: make a confirmation pop up before kicking someone from your league.

EDIT: I would tell him to try and join again the league before posting this but he's not online now and won't be for several hours. Besides, this topic could be used by anyone in a similar situation.