Space Adventures wants the lawsuit thrown out, saying that Enomoto was disqualified because of a chronic kidney-stone condition. They say his money is nonrefundable.
Enomoto claims the kidney stones were an excuse and that he was not allowed to launch in part because he refused Space Adventures' demands for more money.
Enomoto, an eccentric entrepreneur who planned to dress up as anime character Char Aznable, had plans to be the first tourist to do a spacewalk. He spent most of eight months at the Star City training facility near Moscow in 2006 preparing for his flight.
But as disputes arose over how much money Enomoto owed, he was medically disqualified because of his kidney-stone condition. He was replaced by Anousheh Ansari, who became the world's first female space tourist.
Earlier that year, Space Adventures had announced a joint venture with an investment firm founded by the Ansari family. Enomoto claims that he was constantly pressured to invest in Space Adventures while he was a client, and that he was bounced in favor of Ansari in part because the Ansaris agreed to investments that Enomoto refused.
Space Adventures lawyer John Villa said that Enomoto refused doctors' advice to treat the kidney stones aggressively and was well aware throughout the process that the kidney stones could disqualify him.
Villa also said that if Space Adventures provided refunds for medical disqualifications, any would-be space tourist with cold feet could simply provoke a medical disqualification, and collect their payments.
Enomoto's lawyers declined to make their client available for an interview. A Space Adventures spokeswoman also declined comment.
U.S. District Judge James Cacheris will rule later on Space Adventures' motion to dismiss the lawsuit.