DJ Deadmau5 performs at the Xbox One Launch at Milk Studios on November 21, 2013 in Los Angeles, California.
DJ Deadmau5 performs at the Xbox One Launch at Milk Studios on November 21, 2013 in Los Angeles, California. - 

Deadmau5 makes dance music. But he also sells hats, pint glasses, t-shirtsall featuring the eerie, circles-for-ears cartoon "mau5head" that is his symbol. 

"He's in gaming and mobile apps and music and producing and imaging and movies," says his attorney, Dina LaPolt. "He's in every space imaginable."

Under U.S. law, the use of his "mau5head" on all this merchandise has trademark protection, just by existing. But last summer Deadmau5real name Joel Zimmermanapplied for something stronger: trademark registration. 

The implications of registration are significant but limited. "It's a little bit easier and cheaper to sue others," says Jeremy Sheff, law professor at St. John's. 

“There are various side tweaks in the process that a registration is helpful for,” says Rebecca Tushnet, law professor at Georgetown. 

The legal costs, on the other hand, were clear. 

"We always knew Disney would oppose it because that’s what Disney does," says LaPolt. 

Disney is notoriously protective of its intellectual property, especially when it comes to Mickey Mouse. To pick a trivial example, in 1981, Disney successfully got a bar in Colonie, NY called "Mickey's Mousetrap" to change its name, even though it was owned by two men named Mickey.

"We're giving in,'' Mickey Colarusso told the New York Times, ''because we don't have the time or money to battle an organization as big as Disney."

In part, this may be because you need to exercise trademark rights in order to retain them. "Trademark owners often feel they need to take symbolic actions," says Tushnet. 

But despite the certainty that it would bring about a battle with Disney, LaPolt strategized to apply for registration. "I like to change things and battle people," she says. "That’s why I’m a lawyer."

Disney did file to block Deadmau5's registration, arguing that despite the creepy grin and vacant eyes, the "mau5head," with its round head and round ears, "so resembles Disney's prior use and registered Disney's Mouse Ears Marks" as to be likely "to cause confusion, or to cause mistake, or to deceive." 

"There are a number of thing that’ll confuse people," says Jack Jacoby, professor of marketing at NYU's Stern School of Business who says he is involved in 30 or 40 trademark disputes per year.

In the case of Disney vs. Deadmau5,  Jacoby says the confusion case boils down to what’s in the mind of the person who picks a mau5head t-shirt off the rack-and whether they'll think the Deadmau5 item was made by, affiliated with or allowed by Disney.

"Disney’s saying 'Wait, people may think that this comes from us,'" says Jacoby.

Outside a mall in Queens, New York, I put this to the test by showing a picture of a Deadmau5 shirt to various fans of electronic music. 

Among his fans, everyone knew the symbol immediately, and had no confusion about Disney's involvement. 

Jacoby wrote, or at least edited, the book on doing more scientific versions of these surveys for the American Bar Association, and says such a survey could help Deadmau5 if Disney sued for infringement. But although the current battle over registration rights at the Patent and Trademark Office concerns the same questionsDoes the use of the Deadmau5 mark cause "confusion" of Disney's mouse ears markit won't admit this kind of survey. 

"Most of the action is in the federal courts. And the federal courts, they want you to simulate reality as closely as possible," says Jacoby. "But the PTO only wants to look at the mark in isolation. So the silhouette, in this case, of the ears."

This lack of real-world context could hurt Deadmau5's chances. The choice to take on Disney anyways could be to seek a settlement or for PRDeadmau5 has been known for publicity stunts in the past. Or it could be sheer stubbornness. 

"Sometimes people get very committed to their symbols, almost like their children," says Tushnet. 

The Patent and Trademark Office wouldn’t comment on timing, but observers say a decision from the PTO on these warring parents could take years.