The Paralympic champion is currently on trial for murder in Pretoria, South Africa after he shot the South African model through a locked bathroom door at his home in the early hours of Valentine's Day last year.
During the channel's Sunday Night program, footage was shown of Pistorius walking without his prosthetic legs while having his arm outstretched as if to signal holding a gun.
The video has since sparked controversy, but Channel Seven have insisted that they obtained the footage legally and it was only aired in Australia.
The program's executive producer Mark Llewellyn said in a statement: "We would not have run the footage if we thought we had obtained it illegally.
"The material shown on Sunday Night goes to the heart of both the prosecution and defence cases, including the account provided by Oscar Pistorius. The story was run in Australia only and not made available to any other territory."
Pistorius denies murder by maintaining that he mistook Steenkamp for an intruder when he fired four gunshots through the door.