GENEVA (Reuters) - Nineteen U.S. states have introduced bills that would curb freedom of expression and the right to protest since Donald Trump’s election as president, an “alarming and undemocratic” trend, U.N. human rights investigators said on Thursday.

FILE PHOTO: A designated area for protesters is seen outside an event for U.S. Republican presidential candidate Donald Trump at the Savannah Center in Cincinnati, Ohio March 13, 2016. REUTERS/Aaron P. Bernstein

Concerns for free speech in the United States have risen in part because of the Republican Trump’s antagonistic relations with prominent U.S. media, which he has branded “the enemy of the American people” as it has reported on policy missteps and dysfunction in his administration.

The push for stricter laws on expression has come as Trump’s liberal foes have pursued public protest against his policies on issues ranging from immigration to abortion and climate change.

Maina Kiai and David Kaye, independent U.N. experts on freedom of peaceful assembly and expression respectively, said in a statement that the state bills were incompatible with international human rights law.

“The trend also threatens to jeopardize one of the United States’ constitutional pillars: free speech,” they said in a statement, calling for action to reverse such legislation.

“From the Black Lives Matter movement, to the environmental and Native American movements in opposition to the Dakota Access oil pipeline, and the Women’s Marches, individuals and organizations across (American) society have mobilized in peaceful protests,” Kiai and Kaye said.

They said it was their fundamental right to do so, but that bills in Republican-governed states like Indiana, Arkansas, Florida, Georgia, Indiana, Iowa, Michigan and Missouri sought to stop them exercising that right.

The civil rights movement known as Black Lives Matter has been fueled by a series of shootings of unarmed black men by white U.S. police officers that triggered national protests.

The U.N. experts’ statement came a day after they criticized Russia’s treatment of peaceful protesters who took to the streets following allegations of corruption against Prime Minister Dmitry Medvedev.

The U.S. State Department had also criticized Russia’s handling of those protests, calling them an affront to democratic values.

Supporters of the U.S. state legislative action say it sums up the frustration some people feel about protests that get in the way of daily lives, and reflects a wish to maintain public safety. Free speech advocates say the bills are worrying, seeing them as opening the way to criminalizing peaceful protests.

The U.N. experts said several bills proposed in Colorado, North Dakota and Oklahoma targeted opponents of the Dakota Access Pipeline in North Dakota and would have “a chilling effect on environmental protesters”.

Last month dozens of armed U.S. law enforcement officers swept through a protest camp near the site of the pipeline, clearing the gathering that for months served as a base of opposition to the multi-billion-dollar project.

In Missouri a bill proposed a seven-year prison term for “unlawful obstruction of traffic”, while the Minnesota bill would criminalize peaceful protesters for participating in demonstrations that subsequently turned violent.

The U.N. experts said there was no such thing as a violent protest, only violent protesters. “One person’s decision to resort to violence does not strip other protesters of their right to freedom of peaceful assembly,” Kaye and Kiai said.