Tennessee enacted a law Tuesday that critics contend allows public school teachers to challenge climate change and evolution in their classrooms without fear of sanction.

Republican Gov. Bill Haslam allowed the controversial measure to become law without his signature and, in a statement, expressed misgivings about it. Nevertheless, he ignored pleas from educators, parents and civil libertarians to veto the bill.

The law does not require the teaching of alternatives to scientific theories of evolution, climate change and “the chemical origins of life.” Instead, it aims to prevent school administrators from reining in teachers who expound on alternative hypotheses to those topics.

The measure’s primary sponsor, Republican state Sen. Bo Watson, said it was meant to give teachers the clarity and security to discuss alternative ideas to evolution and climate change that students may have picked up at home and want to explore in class.

“I am glad that the governor recognized that this bill does not do all of the things that its critics have alleged,” Watson said Tuesday. “It does not change the state’s science curriculum and it does not change how science is taught. Both of those assertions are red herrings.”

The bill’s critics, which include the Tennessee Science Teachers Assn. and the state chapter of the American Civil Liberties Union, counter that teachers currently have no problem addressing unconventional ideas and challenges that students bring up. They argue, instead, that the measure gives legal cover to teachers to introduce pseudoscientific ideas.

In a statement to the Tennessean newspaper, Haslam said the measure would create confusion over the state’s science standards.

“The bill received strong bipartisan support, passing the House and Senate by a 3-to-1 margin,” he said. “But good legislation should bring clarity and not confusion. My concern is that this bill has not met this objective.”

The law is likely to stoke growing concerns among teachers around the country that teaching climate science is becoming the same kind of classroom and community flash point as evolution. Tennessee is now the second state, after Louisiana, to allow the teaching of alternatives to accepted science on climate change.

“We respect Gov. Haslam for showing leadership in not signing this legislation,” said Hedy Weinberg, executive director of the American Civil Liberties Union of Tennessee. “But that doesn’t change the fact that Tennessee now has a law on the books essentially granting permission for teachers to violate the 1st Amendment by introducing their own personal religious beliefs on the origin of life into the classroom.”

Biologists say there is no scientific controversy over evolution, only a political one.

neela.banerjee@latimes.com