Aerosmith Frontman Steven Tyler's Lawyer Argues He Can't Be Sued For Relationship With 16-Year-Old

Steven Tyler is firing back at the woman suing him for allegedly sexually assaulting her 50 years ago when she was 16 years old ... claiming she can't use his memoir as a weapon in court.

The legendary Aerosmith frontman says his accuser, Julia Holcomb, shouldn't be able to use his memoirs in which he discussed the relationship decades later to sue him for intentionally causing her severe emotional distress.

Julia sued Steven in December, accusing him of sexual assault, sexual battery and intentional infliction of emotional distress.

She claims he first had sex with her when she was 16 and he was 25, impregnating her when she was 17 and pushing her to have an abortion. They were in a relationship for 3 years.

In new legal docs, obtained by TMZ, Steven claims the alleged distress Julia experienced back in 2011 was not a result of his memoir published that year, in which he used a pseudonym to describe their relationship from Tyler's perspective, but rather from a Star Magazine article published months before his memoir was released.

Tyler says he purposefully did not mention Julia by name in his memoirs when he wrote about them having sex back in the day, and he says she's got no problem using their relationship to promote herself in the media.

What's more, Tyler says she waited 11 years to sue him after his memoir was published ... and he says she's barred from suing him for intentional infliction of emotional distress because of a 2-year statute of limitations on such claims.

Tyler also claims his memoirs are a vessel to share his own experiences from his "newsworthy life" ... and he says her IIED claim is therefore barred by the First Amendment.

We reached out to Julia's camp ... so far no word back.