GUATEMALA CITY (AP) — Guatemala’s national police arrested an outspoken opponent of the government Wednesday on charges he falsified documents to form a political party.

Juan Francisco Solorzano Foppa is a lawyer who once served as head of the country’s tax collection agency. In recent years, he has criticized the administration of President Alejandro Giammattei and slammed what he claimed was the political use of law enforcement.

Prosecutors said he was arrested for criminal conspiracy and falsification.

Solorzano Foppa said the charges had been “invented,” and suggested they were retaliation for his criticisms. Guatemala’s legal system and congress have been criticized for protecting those accused of corruption.

“This is not any shame for me. I am proud, knowing that we are doing things right; we are affecting powerful people in the country,” Solorzano Foppa said in a video, in which he showed his handcuffs.

He also shared a video of the moment of his arrest, when his vehicle was cut off by two unmarked cars without license plates. A government official said police sometimes use their private vehicles to make arrests, and that they don't carry license plates for security reasons.

Arrest warrants have also been issued for 14 other people.

Anibal Argüello, a lawyer who once worked for Guatemala's now-defunct U.N.-backed anti-corruption commission, was also arrested.

“This is just the networks of power who we have been fighting for so many years, attacking us,” Anibal Argüello said.

Previously, the government arrested another crusading anti-corruption lawyer, Alfonso Carrillo.

Jorge Santos, who leads the nongovernmental Unit for Protection of Human Rights Defenders, said that in recent days “we have seen a clear attempt to block what the ruling elites led by the government consider to be opponents.”

Opposition congressman Samuel Pérez said “there seems to be a sense of a revenge by those linked to corruption.”

In April, Guatemala’s Congress refused to swear in a crusading female judge to the nation’s highest court, a move the United States condemned.

Gloria Porras won reelection for another five-year term on Guatemala’s Constitutional Court, but she has faced constant challenges apparently linked to her rulings on corruption and other cases.