One club is reacting towards another like little kid

If you are taking something mine, without my approval, I will probably cry and (maybe) I am going to sue you. Little kids are often like that (except for the last part), but the previous sentence translated into reality is described below.
On the first Tuesday of this month Fox sports reported that Real Madrid will sue Inter, and this news became official two days ago. The Italian team desperately wanted to bring Luka Modric, however the opponents warned them that the possible transfer would be violation of financial fair play rule, where the player still have valid contract with the Spaniards for two more years. Now the 'mother' organization (FIFA) can decide whether to interfere in this process, and if Inter is be found guilty, than the club can not sign any new players in two transfer windows plus pay financial fine.