Bubba's father, Howard Ludwig, applied on his behalf after his grandfather gave him a shotgun as an heirloom.

Mr Ludwig said he had not expected to succeed, but he filled in the online form, paid $5 and the licence was his.

US gun laws are regularly the subject of fierce debate, renewed recently after April's Virginia Tech killings.

Gunman Cho Seung-hui was able to exploit a loophole in Virginia state law and obtain weapons despite having a history of mental illness. The loophole was later closed.

Technical problems

The licence includes a picture of a toothless Bubba and a squiggle that represents his best attempt at a signature.

It makes an adorable addition to his baby book

Howard Ludwig

In an article in the Chicago Sun-Times, Mr Ludwig, 30, said that he expected the application to be turned down.

Two rejections did in fact come, he said, but both related to technical problems - on one application he forgot to tick a box stating his son was a US citizen - rather than Bubba's youth.

His third attempt was rewarded with a state firearm owner's identification card (FOID), complete with details of Bubba's height, weight and date of birth.

'No age restrictions'

Illinois gun laws are said to be among the strictest in the US.

But Illinois State Police, who oversee the application process, said that they had followed the law in this case.

"Does a 10-month-old need a FOID card? No, but there are no restrictions under the act regarding age of applicants," the Associated Press news agency quoted Lt Scott Compton as saying.

Mr Ludwig said Bubba's gun would likely remain at his grandfather's house until he was 14.

"I'm not about to approve any unsupervised hunting or trap shooting for Bubba," he wrote in the Chicago daily.

"Still, I'm glad he was able to get his FOID card. It makes an adorable addition to his baby book."