"The cash given to his Parisian clients was gathered from the French Jewish community, wanting to donate to different people and religious schools," said Josiane Stickel-Circurel, who represents a Swiss wealth manager, originally from Morocco, at the heart of the French-Swiss probe.
"He has never been aware of any cannabis trafficking," she told the paper.
The man's arrest was part of a police crackdown in France and Switzerland following an investigation that was launched in February into the smuggling of tonnes of cannabis from Morocco to the Paris region via Spain.
A court on Friday ordered the detention of the main Swiss suspect and his brother, a wealth manager with the HSBC Geneva bank, stressing the gravity of the charges and the risk they would flee.
Their arrests came in parallel with 17 arrests in France last week, with a deputy mayor of a Paris district, Florence Lamblin of the Green Party, among those charged in the case.
According to Swiss media reports, the two brothers are suspected of laundering cash through a Geneva-based finance company, with the possible unwitting participation of French tax evaders.
Lawyer Stickel-Circurel told Le Temps on Monday that her client had knowingly helped tax evaders, "but he had no idea where the money came from."
A raid on the Geneva home of one of the brothers led to the discovery of €800,000 in cash, and 160 watches and jewels worth an estimated €2 million in a hidden safe, Le Temps previously reported.
A third person, a woman working for the main suspect, was also arrested along with the two brothers last Wednesday. She has been set free but must remain available for questioning.
The Swiss group Inter-Community Coordination Against Anti-Semitism and Defamation (CICAD) expressed harsh criticism last week of how several of the country's media described the suspects as "belonging to the Moroccan Jewish community."
The association said the reports could contribute to stigmatizing the entire Jewish community and said it was considering legal action.
CICAD chief Johanne Gurfinkiel told AFP on Monday however that his organization had nothing against the media, quoting Stickel-Circurel's claim that the money under investigation had originated from Jewish donations.
"The media are doing their job when they report the lawyer's words," he said, pointing out that the previous articles did not have grounds to mention the suspects' religious affiliation.