The artworks, bound for an exhibition in Houston, were made by British artist and military veteran Bran Symondson.
"Spoils of War" - a gun covered in $1 bills - "Beat of a Wing" and "Virtue of the Vicious" - guns covered in butterflies - have all been banned from entering the US, although the state of Texas has an "open carry" law, which allows people to carry shotguns and rifles in a non-theatening manner.
Mr Symondson, who served in Afghanistan, now works as a reportage photographer and artist.
The 2011 Amnesty International Media Award winner said the guns for the art were captured en route from Afghanistan to Syria and were no longer able to be used as weapons.
"It is ironic that the law permits US citizens to go and buy a new, live weapon which I could, in theory, use to create one of my artworks from, which then could technically be used in its intended form but will not allow my pieces of harmless art into the country," he said.
Within "Virtue of the Vicious" there are clear 7.62 empty rounds which each hold a filing representing the history of Texas, including a yellow rose petal which symbolises the yellow rose of the state, and a pink cloth with a blood stain to represent that jacket that Jackie Onassis wore when former president John F Kennedy was assassinated.
Maddox Gallery confirmed in a statement that the artworks had been halted at US customs and will not be released.
The same London-based gallery came under fire after it displayed a nude painting of Donald Trump by artist Illma Gore. The painting, called "Make America Great Again", was banned in the US.