That's right. You can't have it. At least not if you manufacture clothing. At least not if you live in the US. This is what the United States of America Patent and Trademark office says. It happened on the 28th of January, 2014. While all the mathematicians were trying to unravel the mysteries of the universe a clever guy from Brooklyn in US decided to go to the patent office and copyrighted the 3000 years old Greek letter. As we all know anything that the US says goes because everybody's too afraid to be sued by US lawyers. This means that a guy in US de facto owns the letter pi worldwide if it comes down to its use in apparels. For more information you can read the article "This guy trademarked the symbol for pi and took away our geeky T-shirts" in Wired Magazine.
This is yet another retarded idea from the same people that brought you the DMCA (digital millennium copyright act) in terms of copyright laws regulations and associated complications. The problem with this point of view is that it originated in US which means that the power elite is using all its connections to the US government to spread out the same nonsense throughout the world.
Such stupid ideas of copyright are right there with the same stupid notions as patenting or copywriting human DNA.
We have explained in many articles (poor example see Intellectual Property Rights Are Dumb and Knocking Down Intellectual Property Rights) why intellectual property rights (IPRs) are pure nonsense. This is yet another example as to how and why governments cannot be trusted.
The only meaningful solution for such a degree of stupidity is to get rid of all governments and with them their very soul. In a truly free market this would never be allowed simply because there is no contractual relationship between the manufacturer of these clothing and everybody else on the planet. It is true that this person may choose to have a contract with its clients but this is a purely voluntary agreement. What is not voluntary is an imposed contract between this person and everybody else just because this person made it to a government office, filled in some paperwork and pay the fee.
It is now your turn to make up your mind. Would you like this nonsense to continue? Or would you prefer to have a much more rational system where everybody is free to use ideas as they see fit? Don't kid yourself. If you believe that the future is not at stake you are sorely mistaken. The future, your future, it's always at stake when it comes to government actions. However, it is not up to us to decide, you are free person that must make up their own mind as you go on.
Note: please see the Glossary if you are unfamiliar with certain words.