An anti-abortion minister is suing Yellowstone County and state officials in federal court over alleged violations of his free speech and other rights when he was arrested while collecting petition signatures at MetraPark.

Calvin Zastrow, a Billings resident and minister for the Assemblies of God, claims that his arrest Feb. 4 at MetraPark’s Montana Pavilion was illegal. His suit also challenges as unconstitutional an obscure state election law on coercion or undue voter influence that limits the speech of ministers, clergy and church regarding candidates and ballot issues.

Zastrow’s attorney, Matthew Monforton of Bozeman, said, “Cal was arrested under suspicious circumstances, to put it charitably.”

Zastrow’s suit challenges what Monforton called Montana’s “clergy censorship law,” his illegal arrest and MetraPark’s illegal exclusion of “pro-life signature gatherers.”

The suit, filed Tuesday in U.S. District Court, names as defendants Attorney General Steve Bullock, Secretary of State Linda McCulloch, Political Practices Commissioner James Murry, Yellowstone County, County Attorney Scott Twito, Deputy County Attorney Kevin Gillen and three unnamed Yellowstone County sheriff’s deputies.

All defendants contacted said they had not seen the suit and declined to comment.

The case has not been assigned to a judge.

Zastrow was at MetraPark gathering signatures to quality for the 2012 ballot Constitutional Initiative 108, which seeks to amend the state’s constitution to define unborn children as persons, the complaint said. Zastrow tried to convince voters that they have a religious duty to support pro-life initiatives and candidates, the complaint said.

Zastrow went to an area near the Pavilion, where a Family Life Expo was being held, to collect petition signatures. Monforton said the area is commonly used to collect signatures.

After about an hour and a half, a MetraPark official told Zastrow to move to another location, which limited his access to the public and said he was on private property, Monforton said.

Zastrow replied that the property was public and declined to move.

Sheriff’s deputies eventually arrested Zastrow on trespassing charges and booked him into the Yellowstone County jail. He was released a few hours later and told that MetraPark was dropping the charges, Monforton said.

The arrest violated Zastrow’s rights to free speech, probable cause and equal protection, the suit said.

County officials did not claim that Zastrow had violated the election law limiting the speech of clergy, Monforton said. But Monforton questioned the arrest of “a pro-life missionary” who was exercising the same rights as others, who have not been arrested while seeking signatures for petitions in the same place.

Zastrow’s suit seeks to prevent the defendants from threatening to enforce the state law addressing clergy speech and from obstructing Zastrow from lawfully gathering signatures at MetraPark. He also is seeking a jury trial along with unspecified compensatory and punitive damages.