Three Court of Appeal judges rejected a challenge by EPE, of Memphis, Tennessee, to an earlier court ruling in favour of Sid Shaw, who runs a memorabilia shop called Elvisly Yours.
Mr Shaw, whose shop in the Trocadero Centre in London'sPiccadilly Circus sells articles from watches to toiletries that bear the singer's name, won a ruling from a High Court judge in March 1997 that EPE did not have the sole right to Elvis Presley's name.
After that ruling EPE took their case to the Court of Appeal, challenging the decision by Mr Justice Laddie that a celebrity's name, whether they are living or dead, cannot be used as a trademark.
His ruling led to the rejection by the Trade Mark Registry of an application to register Diana, Princess of Wales.
At the Court of Appeal in London yesterday, Lords Justices Simon Brown, Morritt and Walker gave their decision in a case which lawyers say has "wide commercial importance in the trademark world".
Mr Shaw said that today's judgment "will have a far-reaching effect on all stars and celebrities living or dead".
EPE was refused leave to appeal to the House of Lords by the three judges, but it can still apply directly to the Law Lords themselves to hear the case.
A jubilant Mr Shaw said after the ruling: "I'm delighted. I've proved that Elvis belongs to all of us - Elvis is part of our history, part of our culture.
"They tried to put me out of business and they haven't succeeded. I'm still here."
In rejecting EPE's appeal, Lord Justice Brown said that there should be no "assumption that only a celebrity or his successors may ever market his own character".