The lawyer of the Croatian prodigy Alen Halilovic does not believe the transfer of his client from Dinamo Zagreb to Barcelona is in any danger, despite the Fifa sanctions taken against the Spanish club.

Barça have announced that they will appeal after being hit on Wednesday by a year-long transfer ban for of contravening rules relating to the "international transfers of non-Spanish minors". However the Belgian Jean-Louis Dupont – who was part of the legal team that led to the Bosman ruling in 1995 – believes the deal for the 17-year-old, which was announced last week, will still go ahead because it has already been completed.

"I cannot foresee for one second that my client, Alen Halilovic, will not be able to play for Barça," he said in an interview with the Spanish radio station RAC1 on Thursday. "This is an operation that has been completed prior to the sanction."

Dupont was instrumental in the landmark case that ended restrictions on movement of players between clubs after Jean-Marc Bosman was prevented from joining the French side Dunkerque. He has also represented a host of high-profile football clients in the past but believes the sanctions against Barcelona have gone too far.

"Fifa has done well to identify a problem, by I think they're trying to apply the wrong medicine," Dupont said. "When this Fifa ban doesn't allow for the future of a child and his family, then the regulation is mistaken. I have no doubts, that if Barça were to sign an 11-year-old, they would guarantee proper education and the correct social environment."

Barcelona's president Josep Maria Bartomeu said that his club were victims of a "grave injustice", adding: "We are outraged.

"With this sanction, Fifa is punishing a model that has existed for 35 years and which is the essence of this club. We are not prepared in any way to give up our educational model. We have defended, continue to defend and will always defend the rights of minors."

He defended the club's La Masia academy, saying: "Hands off La Masia, that's the message we want to send to our members and fans, hands off La Masia.

"We will fight until the end to protect this model because it has made our first team become a leader in world football. We have absolute confidence in our lawyers and they tell us we have good grounds to think that the sanction will be lifted."