Judges in Perpignan, a city in the south of France, issued the ruling after a couple tried to tie their newborn's name in with British royalty.
First the judges blocked the use of the name by these parents, then they called for a legal ban on using Prince William as an extended first name.
To explain the reason for the ban the judges referred to Article 57 of the civil code.
A French legal source told the Mirror: "[The code] allows judges to protect a child from a potential lifetime of mockery by overruling the parents."
After the prosecutors ruled out Prince William as a name for the child, the parents allegedly asked if they could name their child Mini Cooper instead.
This, as you can guess, was also banned.
In January this year, another bizarre baby named was banned in France after parents wanted to call their child Nutella.
Yep, the same name as the chocolate spread.
According to the BBC, the judge ordered that the child be called Ella instead.
He said: "And it is contrary to the child's interest to have a name that can only lead to teasing or disparaging thoughts."