Usman Hamid, a human rights campaigner, told Al Jazeera the murder case was an important test for the government of Susilo Bambang Yudhoyono, Indonesia's president.
"Only when the real masterminds of the murder are brought to court, can the government prove that even the most powerful in Indonesia are not above the law," Hamid said.
The same court that acquitted Priyanto overturned the acquittal on Friday based on new evidence and ruled he had committed premeditated killing, a court spokesman, said.
Priyanto was also convicted of using forged documents to board the plane posing as a security agent. He was sentenced to a total of 20 years in prison.
Al Jazeera's Step Vassen met Priyanto shortly on Friday before he was arrested.
Priyanto said: "I will never give up my fight. I did nothing wrong. I didn't know Munir. I had nothing to do with him. I didn't even know him, he was not my friend nor my enemy. It is not my business."
More than a dozen security officers took Priyanto from his home on the outskirts of Jakarta and brought him to Cipinang Prison late on Friday.
Munir's widow has been fighting an uphill battle for more than three years to bring the perpetrators of her husband's killing to justice.
"The police say they will wait for official documents from the supreme court before they take any further steps," Suciwati told Al Jazeera.