Turns out you can't have your "pi," and eat it too.

In January 2014, a Brooklyn artist named Paul Ingrisano trademarked the 3,000-year old mathematical symbol "π" followed by a period, and is actively protecting his mark, Wired's Kevin Poulsen reports.

Ingrisano, who uses the design on shirts he sells through his company, PI Productions Corp., reportedly discovered that the custom t-shirt printing site Zazzle was selling merchandise featuring the pi symbol, and had an attorney send a cease-and-desist letter to the site (see below).

Zazzle initially complied with the request by banning thousands of "pi"-related garments from its shop, but reversed course after receiving complaints, according to Wired.

Sellers in Zazzle's online forum were understandably infuriated by the temporary removal of their merchandise. One user wrote, "Again, please explain how one person's trademark which incorporates a generic, untrademarked mathematical symbol can be justification to remove all designs using this generic symbol?"

"I am enraged! Here many of us are trying to spread the mathematical truth ... and some lunatic thinks he owns part of the Greek language and its usage as part of the language of the universe!" another wrote.

According to Wired, Ingrisano and his lawyer are planning their next move.

Zazzle Pi Trademark Letter