A 10-year-old ban on buying military-style assault weapons in the U.S. expired Monday, giving Americans the opportunity to once again legally purchase the guns.

The Bush administration came under fire from gun control advocates and Democratic presidential candidate John Kerry for not renewing the ban, which outlawed 19 types of military-style assault weapons.

A number of national police organizations also wanted to see the ban renewed.

Sarah Brady, whose husband James was Ronald Reagan's press secretary until he was shot and injured during the 1981 assassination attempt on the then-president, said that not reauthorizing the ban is "purely political."

"The real onus fell on President George W. Bush," she told CBS-TV's The Early Show. "He has exerted absolutely no leadership. We have a president and leadership in the House and Senate that simply do not want to face this."

In 1994, then-president Bill Clinton signed the ban on military-style assault weapons, but included a clause that would see it expire if it wasn't renewed by Congress.

But some argue that guns similar to those banned were still making it to market anyway, with a name or feature changed, because of a loophole in the law. And weapons such as AK-47s and Uzis continue to be banned under a 1989 law, while a number of states have also introduced their own ban on assault rifles.

"To lead anyone to believe we're talking about a class of guns that's more powerful, makes bigger holes, shoots more rapidly is not true," Wayne LaPierre, head of the National Rifle Association, told CBS of the guns that will now be available for sale.

American gun shop owners agreed, saying the guns available for sale last week are similar to the ones included in the ban. They said the only difference gun buyers might see is reduced prices, as the guns move back into the mainstream.

The Brady Campaign to Prevent Gun Violence points out that the Washington snipers used a military-style assault weapon when 10 people were shot in 2002.

The Brady Handgun Violence Prevention Act, which requires those buying guns to have federal background checks, is still in effect.