Ramon Olorunwa Abbas – known to his 2.5 million Instagram followers as Ray Hushpuppi – and another cyber-heist suspect Olalekan Jacob Ponle (aka Mr Woodberry) were arrested in Dubai, where they lived, in June.
They then appeared in a Chicago court on 3 July.
The United Arab Emirates has no extradition treaty with the United States but Dubai police said they had been extradited to the US.
A spokesman for the US Department of Justice said that Hushpuppi was expelled from Dubai and was not extradited. He did not answer how he ended up in US custody.The Chicago defence lawyer’s argument that Hushpuppi was paid by designer brands for promotion has set the stage for what promises to be a long trial in American courts.
The Federal Bureau of Investigation (FBI) accuses Mr Abbas, 37, of conspiring to launder hundreds of millions of dollars from frauds known as Business Email Compromise (BEC) and other scams.
It is the latest high-profile fraud case involving a Nigerian national in the United States but his lawyer says the US had no authority to transport him from Dubai.
“In my opinion, the FBI and the government here acted illegally when they kidnapped him from Dubai without any legal process to do so,” Mr Pissetzky told the BBC.
“There was no extradition, there were no legal steps taken, there were no court documents filed, it was simply a call to the FBI. He is not a citizen of the United States, the US had absolutely no authority to take him,” his lawyer says.
But the Dubai police said in a Facebook post that the FBI director had thanked them for extraditing the two men.
“You’ll have to ask them about why they called it an extradition,” the US Department of Justice (DoJ) spokesman responded in an email.
In a statement about Mr Abbas initial court appearance, the DoJ said “FBI special agents earlier this week obtained custody of Abbas and brought him to the United States” without giving any further details.
Mr Pissetzky is not convinced.
“If Dubai wanted to expel him, they should have expelled him back to Nigeria. I’ve never heard of anything like that. That is the real story here.”