With President Obama's visit to Colorado to rally support for gun control measures, some of the state's sheriffs are speaking out against more restrictions.

More than a dozen sheriffs held a press conference Wednesday in a Denver park near where the president met with law enforcement and community leaders to discuss the gun control package recently signed into law by Gov. John Hickenlooper.

Justin Smith of Larimer County was among sheriffs who gathered in advance of Obama's visit. He and other sheriffs are slamming new regulations on firearms as unconstitutional.

Smith dismissed Obama's visit as "a slap in the face to all Coloradans."

He told The Denver Post that multiple Denver police officers told him they had no choice in attending Wednesday's event with the president, suggesting that there would be repercussions for attending the protest.

Smith accused the president and Democratic lawmakers of exploiting the shootings in Aurora and Newtown, Conn. and said Colorado's new gun bill won't prevent similar acts of violence, KDVR.com reported.

Colorado has gone further than any state outside the Northeast in passing new gun laws. The state now prohibits the sale of magazines that hold more than 15 bullets and requires background checks for all private gun sales.

El Paso Sheriff Terry Maketa criticized Obama and Hickenlooper for "ram-rodding" the new gun restrictions through the legislature, according to The Denver Post.

"Our governor has lied to the citizens of this state," Maketa told a about 30 protesters at Denver's Fred Thomas Park, according to the Post's report.

The County Sheriffs of Colorado, a Littleton-based advocacy organization, released a position paper on the day of the president's visit, arguing that gun control does not result in lower crime rates.

"[W]e urge our state elected officials not to make decisions during this grieving period because it would likely lead to policies that are unenforceable and possible unconstitutional, while punishing law abiding citizens and doing nothing to reduce violent crime," the paper read.

Broomfield Police Chief Thomas Deland, president of the Colorado Association of Chiefs of Police, told KDVR.com that his group supports the state's new restrictions on high-capacity magazines and expanded background checks.

Obama noted during Wednesday's visit that more than 100 days have passed since the shooting rampage that killed 20 first-graders and six adults at an elementary school in Newtown and reignited the national debate over access to guns.

"Every day that we wait to do something about it even more of our fellow citizens are stolen from our lives by a bullet from a gun. Now the good news is Colorado has already chosen to do something about it," he said.

Obama's trip comes a day after a study commissioned by the National Rifle Association, which has opposed Obama's gun control measures, recommended that schools have trained, armed staffers to increase security for students. The American Federation of Teachers denounced the proposal.

The Associated Press contributed to this report.

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