FILE - In this Nov. 11, 2016, file photo, more than 500 clergy from across the country gather for a "Clergy for Standing Rock" march on N.D. Highway 1806 near Cannon Ball, N. D. Attorneys for oil pipeline opponents are fighting an attempt by a South Dakota sheriff to be dismissed from a lawsuit challenging new state laws that aim to prevent disruptive demonstrations against the Keystone XL pipeline similar to those against the Dakota Access oil pipeline in North Dakota. Plaintiffs' attorneys in a lawsuit spearheaded by the American Civil Liberties Union argue Pennington County Sheriff Kevin Thom will be enforcing law that infringes on free speech. Thom's attorneys say he must enforce state laws but isn't responsible for defending them. (Mike McCleary/The Bismarck Tribune via AP)

BISMARCK, N.D. - Attorneys for oil pipeline opponents are fighting a South Dakota sheriff's attempt to be dismissed as a defendant in a lawsuit challenging new state laws that aim to prevent disruptive demonstrations against the Keystone XL pipeline.

Pennington County Sheriff Kevin Thom should remain a defendant in the suit spearheaded by the American Civil Liberties Union because he will be enforcing law that amounts to an unconstitutional infringement on free speech, an attorney for the plaintiffs argued in a Tuesday court filing.

The Republican-backed legislation passed in March allows officials to pursue criminal or civil penalties from demonstrators who engage in "riot boosting," which is defined in part as encouraging violence during a riot.

Supporters of the legislation sought to head off protests of the Keystone XL like those mounted against the Dakota Access oil pipeline in North Dakota in 2016 and 2017. North Dakota spent $38 million on policing those protests, which resulted in 761 arrests over a six-month span.

The ACLU is suing South Dakota Gov. Kristi Noem, Attorney General Jason Ravnsborg and Thom in federal court on behalf of activists. An attorney for Thom last month asked that the sheriff be dismissed from the lawsuit, saying he must enforce state laws but isn't responsible for defending them. Attorney Rebeca L. Mann also argued that Pennington County shouldn't have to defend state laws that it doesn't have the power to change.

Plaintiffs' attorney Brendan Johnson countered in Tuesday's court filing that "each time Thom makes a choice about the laws' meaning, as the highest official in the county for that action, he is doing so as a policymaker for Pennington County."

Johnson also argued that Thom must use his own discretion when enforcing the law, making him an "appropriate defendant."

Pennington County is one of eight South Dakota counties along the route of TC Energy's planned Keystone XL pipeline to move Canadian crude through Montana and South Dakota to Nebraska, where it would connect with lines to Gulf Coast refineries. The $8 billion project has the backing of President Donald Trump but is being fought in the courts by opponents.

The ACLU of South Dakota, North Dakota and Wyoming said it named Thom as a defendant in the lawsuit because he's sheriff in the county in which the activists are working. Plaintiffs include the Rapid City-based NDN Collective non-profit, which advocates for indigenous peoples and climate change awareness.

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News from © The Associated Press, 2019