This is a little bit into my gray area. I disagree with the judge but I can see his point even if he overstates it with the shirt in question:

"The impact of violence is so great that it now has equal importance as the issue of illegal drug use in schools," U.S. District Judge James Knoll Gardner wrote in an opinion handed down this week.

"There is nowhere that is truly safe or immune from the problem of school violence, from the one-room schoolhouse to America's largest universities," Gardner said.

"Students," he said, "have no constitutional right to promote violence in our public schools."

What this judge apparently doesn't understand that his own orders are carried out with the threat of violence. There is illegal violence and there is legal, even praiseworthy violence. I don't see that the shirt advocated anything illegal or immoral:
 

According the court order and the article the complete text on the back of the shirt says, "Special Issue-Resident-Lifetime License--United States Terrorist Hunting Permit--Permit No. 91101 Gun Owner-No Bag Limit". The front of the shirt has a gun on the pocket which has a gun and says, "Volunteer, Homeland Security".

And how does this "promote violence in the school system"? It is promoting the rapid stopping of illegal violence using legal violence. If the shirt advocated hunting Muslims, blacks, Jews, or some other ethic, racial, or religiously identified group I would agree with him. But not this. Terrorists are not, or at least shouldn't be, a protected group.

I must conclude this is another case of simplistic minds either refusing to or being unable to see the total picture.