The American Center for Law and Justice, an offshoot of Pat Robertson's Christian Broadcasting Network, filed a lawsuit Tuesday in U.S. District Court contending the suspension violated Hosier's rights to free speech and religious expression.
The center took on the case for free, saying it was "deeply offensive" for the school district to call all rosary beads gang symbols. The lawsuit was filed on behalf of Hosier and his mother, Chantell Hosier, against the Schenectady City School District and school officials, including the middle school's principal.
A district spokeswoman did not immediately return a telephone call seeking comment Tuesday.
The lawsuit asks the court to declare the school's dress code and Hosier's suspension unconstitutional. It requests a jury trial.
Hosier received a one-week suspension for refusing to take off his prayer beads or hide them under his shirt two weeks ago.
Hosier, saying he won't go to school without the rosary, was suspended again last week when he returned to school with it.
Judge Lawrence Kahn ordered Hosier reinstated pending the June 11 hearing.
Other school districts have punished students for wearing rosaries. In February, a 14-year-old boy in Haverstraw, in southeastern New York, was suspended for a day for wearing a rosary. And in Texas, a Dallas high school student was told to stop wearing her rosary in September 2008.
In recent years, rosaries worn by celebrities including Lindsay Lohan, Britney Spears, Dakota Fanning and soccer star David Beckham have made the Catholic prayer beads popular as jewelry.