This Brooklyn artist just won't let anyone have a piece of his pi. Paul Ingrisano has trademarked π. – pi followed by a period – with the US Patent and Trademark Office, and is now threatening legal action against clothing brands who use the mathematical symbol. 

The copyright troll, who registered the trademark under his company, Pi Productions Corp, sent a cease and desist letter to Zazzle, a print-on-demand clothing company which regularly features pi on its clothes. Pi may be an ancient letter of the Greek alphabet, but it's Ingrisano's now – and he wants it all for himself.

"It is important that Ingrisano exercise his right to protect his trademark," his attorneys argue in the letter. "It serves as an important and distinctive representation of the origins of his products as well as the goodwill of his company." 

Fearing a lawsuit, Zazzle responded by temporarily pulling all its pi-related items of clothing from the site – a move which sent its many independent designers into a frenzy.

"This would be like McDonald's claiming the letter M as a trademark," writes Jez Kemp, who sells pi-related merchandise on the site. "The trademark is in the combination of style and symbol, not the symbol itself."

Zazzle has since restored the items and thrown out Ingrisano's claim against the company. But how did Ingrisano manage to trademark pi (or at least, pi with a dot after it) anyway? Pi pre-dates Paul Ingrisano by thousands of years. His attorney claimed that many Zazzle products "were confusingly similar to his client’s design". No shit, it's a 3,000-year-old symbol.

But it looks like Ingrisano isn't done with copyright trolling – he's also put in a request to trademark I<3 for himself. One would imagine the patent office would be on red alert after the mess with pi.