Saad al-Ajmi, information minister between 1999-2000, was detained at the airport as he, his wife and daughter were trying to leave for a pilgrimage in Saudi Arabia, Al-Humaidi al-Subaie said on Twitter.
He said Ajmi, a professor at Kuwait University and contributor to several Gulf newspapers, was sentenced Thursday for an article published by the pro-opposition Al-Aan electronic newsletter about two years ago about alleged government corruption.
The court also passed the same sentence on writer Zayed al-Zaid, who co-owned Al-Aan with Ajmi, on a complaint by Finance Minister Anas al-Saleh, the lawyer said.
There was no immediate report whether Zaid had also been arrested.
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The lawyer said the verdicts were issued in absentia and that neither he nor his clients were informed of the case or the ruling.
The verdict was sent for immediate implementation although such a process normally takes several weeks, he said.
Subaie said he plans to challenge the ruling on Sunday.
On Tuesday, authorities arrested former liberal MP Saleh al-Mulla for comments on Twitter deemed offensive to the emir and Egyptian President Abdel Fattah al-Sisi, who visited Kuwait last week.
Mulla has been in detention since then and is due for trial on Sunday.
Kuwaiti courts have sentenced several opposition activists and former lawmakers for remarks deemed insulting to the emir.