So the Church ruled that Ted Kennedy was guilty of fraud and deception in the taking of marriage vows, then the vows were defective, and consequently, fell short of being sacramental.
A legal or civil "marriage" existed, but not a sacramental one, because a sacramental one must be based on true consent.
By way of analogy, it's the same as if you lied and only pretended to be baptized, or practiced fraud or forgery in the signing of a contract. Such a "baptism" or such a contract would be null and void.
In this case, the Church said "Ted, you never intended fidelity from the git-go, your marriage vows were a sham." I must say, the Church was right about that.