Retailers across the UK who sell airguns must now be registered firearms dealers, under a change in the law.
The SNP government welcomed the new curbs
Dealers must conduct face-to-face sales and record buyers' names and addresses, plus details of the weapons sold.
The Scottish Government said communities had been "crying out for action" to take weapons off streets.
Sharon McMillan's son Andrew Morton, two, died after being hit in the head with an airgun pellet in Glasgow. She said the new law was "hopeless".
Mark Bonini was sentenced to life imprisonment for Andrew's murder in the city's Easterhouse area two years ago.
Ms McMillan said: "Are the police going to be standing at every shop corner to make sure these guns are licensed?
"Are they going to help? I don't think so.
"I just really don't think it's gone far enough, I think it's hopeless. It's not going to do any good raising the age."
The minimum legal purchase age for air weapons has also now risen to 18.
Ms McMillan said that "won't do any good".
Two-year-old Andrew Morton was killed by an airgun
The SNP administration, which supports a licensing scheme, has maintained its call for powers over firearms to be devolved to the Scottish Parliament.
Scottish Justice Secretary Kenny MacAskill said: "If you are over 18, if you can an show identification to the appropriate registered firearm seller then you can acquire an air weapon.
"That trust is unacceptable.
"That's we we've entered into discussions with the Westminster government to ask them to give us the powers so we can legislate, so we can make quite certain that the only people who can acquire an air weapon - which after all kill or main indiscriminately - are those who have a legitimate purpose."
Tayside Chief Constable John Vine, who speaks on firearms issues for the Association of Chief Police Officers in Scotland (Acpos), said he believed the changes were enforceable.
"We look forward to working with the Scottish Government to monitor their effectiveness and to consider what other steps could be taken to reduce the harm caused by dangerous weapons," he said.