Bosses at Arrow Productions, who own the rights to Deep Throat, launched legal action last year (13), just weeks before the release of Lovelace, a film about the adult movie's star with Seyfried in the title role.
They claimed clips from the porn film were used in the biopic without permission and infringed their copyright. They also alleged Lovelace was too similar to their own film and sought $10 million (£5.8 million) in compensation.
New York District Judge Thomas Griesa dismissed the case on Tuesday (26Aug14) and ruled the two films are completely different as one is biographical while the other is porn.
He wrote in his ruling, "Lovelace has an entirely different purpose - it is a critical biographical film. Thus, given that the two films have entirely different purposes, it is impossible that defendants' could have copied the core of Deep Throat."
He added that the use of old footage put a "new, critical perspective on the life of Linda Lovelace and the production of Deep Throat" and did not tarnish the reputation of the original movie.
Officials at Arrow Productions are considering an appeal against the ruling. They previously tried to block the distribution of Lovelace last year (13) but a judge denied their request.