Zaki Bani Rsheid, who appeared in a blue prison jumpsuit at Amman's state security court, denounced his arrest and trial in a military tribunal as unconstitutional.
"I reject this trial and my presence here before the state security court. This court does not have the jurisdiction to look into my case," Rsheid told the judge from the dock.
Rsheid was arrested last month and accused of "acts that could harm Jordan's relation with a brotherly state" after he criticised the UAE for blacklisting more than 80 Islamist groups.
In comments published on his Facebook page, Rsheid described the UAE as "the prime godfather of terrorism" and accused the energy-rich Gulf state of serving US and Israeli interests in the region.
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Rsheid and his legal team insisted that the accusation against him falls under the jurisdiction of a civilian court, not the state security court.
But the state prosecutor said that any act that undermines Jordan's relations with another country falls under the country's anti-terrorism law.
Jordan is a close ally of the UAE and both are part of the US-led campaign against the Islamic State group that currently controls swathes of territory in Iraq and Syria.
Organisations blacklisted by the UAE include Al-Qaeda, IS, Yemen's Shiite Huthi militia and the Muslim Brotherhood -- which was formed in Egypt and has branches across the region.
The Jordanian branch of the Muslim Brotherhood is the main opposition force in the kingdom and has wide grassroots support.