Visitors at CES 2016 on Thursday watch an unexpected stunt as two U.S. marshall appeared and raided booth belonging to Changzhou First International Trade. The federal officers seized an alleged counterfeit hoverboard along with its promotional materials.

Bloomberg reported that the raid was a result of weekslong effort by Future Motion, a Silicon Valley startup. The company holds a patent of a self-balancing electric skateboard called Onewheel which looks very similar to the ones that was confiscated by federal agents.

CES as the annual biggest electronic trade show in America, according to Bloomberg, has always been full of small-bore dealers, many from China in small booths. Consumer Technology Association (CTA) is the trade group that manage the show and rent the booth to anyone that pay the fees. However, some companies often encountered the booths sell counterfeit products, thus infringed their patent and trademark.

According to Business Insider, Onewheel originally started as a side project. The electric skateboard was invented by Kyle Doerksen. He founded the Future Motion Inc in 2013 and launched its kickstart campaign in 2014 and successfully raised $630,000.

Future Motion also registered for its technology and design. Last August, the company has its patent for its technology approved, and its design patent has also been approved earlier this week. The patent secured technology and design thus prohibiting competitor to produce a look-alike product.

Changzhou First International Trade was first noticed under the radar last year. Doerksen received a tip from one of Onewheel users who saw a Chinese company offered similar boards in Alibaba online marketplace to retailers. Some retailers in Iceland, Germany, and the U.S has bought the knock-off products according to Alibaba.

Regarding the raid, a lawyer for Future Motion, Shawn Kolitch told Bloomberg, "Would we have done this without the design patent being issued? The answer is we wouldn't have bothered." He also challenged the alleged counterfeit producer, "If you can show the design patent drawing next to an accused product side by side, and they look identical, it helps your case."

Gizmodo reported that Onewheel boards go for $1,500, while the Trotter boards were being marketed to retailers at $500.

In regard to copyright and patent dispute, legal department of CES has issued a guideline to solve the issue during the trade show. CTA trade group also suggested companies to bring only one lawyer, one translator and two employees to clarify the legal issue. In the federal raid at the Changzhou First International Trade booth, Future Motion sent six lawyers accompanying two federal law enforcement agents on court order.