A law to allow public school teachers to challenge the scientific consensus on issues like climate change and evolution will soon take effect in the southern US state of Tennessee.
Tennessee Governor Bill Haslam allowed the bill -- passed by the state House and Senate -- to become law without signing it, saying he did not believe the legislation "changes the scientific standards that are taught in our schools."
"However, I also don't believe that it accomplishes anything that isn't already acceptable in our schools," he said in a statement.
The measure allows teachers to "help students understand, analyze, critique and review in an objective manner the scientific strengths and scientific weaknesses of existing scientific theories covered in the course being taught."
It also says the legislation "shall not be construed to promote any religious or non-religious doctrine."
In recent days the governor had received a petition signed by more than 3,000 people urging him to block the bill, but its conservative backers had enough support to override a veto with a simple majority.
"Good legislation should bring clarity and not confusion. My concern is that this bill has not met this objective," Haslam said. "For that reason, I will not sign the bill but will allow it to become law without my signature."
Critics have labeled the legislation the "Monkey Bill" in reference to the highly publicized 1925 "Scopes Monkey Trial" in which Tennessee charged high school science teacher John Scopes with violating a state law against teaching "that man has descended from a lower order of animals."
The Tennessee Science Teachers Association and the state chapter of the American Civil Liberties Union, the measure's biggest critics, said it would provide legal cover for educators to teach pseudoscientific ideas.
"They are not talking that much about creationism but rather about Intelligent Design," Hedy Weinberg, executive director of the ACLU's Tennessee branch, said earlier this week.
"It's a very nuanced and clever way... to challenge the theory of evolution and allow teachers to inject Intelligent Design and neo-creationism."
Intelligent Design is the idea that scientific evidence can show that life forms developed under the direction of a higher intelligence.
The Discovery Institute, whose model legislation inspired the bill, had hailed it as "protecting the academic freedom of science teachers to fully and objectively discuss controversial scientific topics, like evolution."
Based in Seattle, the group backs the teaching of alternatives to evolution in public schools and supports research into Intelligent Design.
The latest controversy is part of a long-running battle between advocates of secular public schooling and conservative Christians who accuse authorities of infringing on their freedom by keeping religion out of the public sphere.
A Gallup poll in December 2010 found that four in 10 Americans believe God created humans in their present form some 10,000 years ago.
Scientific evidence shows that humans evolved from ape-like ancestors over a period of roughly six million years.
In 1968 that the US Supreme Court ruled it was unconstitutional, based on the separation of church and state, to ban the teaching of evolution.
Explore further: Tennessee seeks to question evolution in bill