I found this on Wikipedia. A little difficult to read as I think a person with english as their second language wrote it.
On Feb 12, 2008, FilipoviÄ‡, announced to visit Japan on his blog. With the foundation of the new MMA event, 'DREAM', co-established by FEG running K-1 Hero's and the former Yarennoka! organizing committee members which had managed PRIDE FC, FilipoviÄ‡ officiates ending his career in UFC and the participation into the new event.
After much speculation and many possible rumored opponents, (including Yoshihiro Nakao and Dong Sik Yoon), Fight Entertainment Group confirmed on March 11, 2008 that Cro Cop would be facing Tatsuya Mizuno at DREAM.1 on March 15, 2008 at Satiama Arena, in Japan. 
When asked about the Croatian's current contract status with the UFC and whether it would interfere with his participation in 'DREAM' events, DREAM producer and front man Keiichi Sasahara said, "Though I can't share specific details about his contract, there will not be any foreseeable problems arising."
The 2006 Pride Grand Prix champion was vague in answering the question himself, qualifying his response by mentioning his intent to return to the American MMA giant sometime in the future.
"Well, as you all know, I had a bad period in my last two fights, which I'd lost in the UFC," Filipovic said. "I don't want anyone to think that I'm running away from the UFC, but I was thinking a lot about how to continue with my career, and I think in this moment, I think Dream is the right place for me."
"Another thing is that I never liked fighting in the cage. I always liked to fight in the ring. The second thing is that I liked fighting in Japan. Japan is like my second home -- I feel like I'm home in Japan. All those reasons [have brought me] here, and I'm very happy that I'm going to fight here in Japan. But of course, one day, I don't know when, but definitely I'll be back in the UFC to show that it was just a bad period for me. Now I'm fully recovered, physically and mentally, most important mentally."
On March 15th, 2008 he defeated Tatsuya Mizuno by TKO in the 1st round.
Filipovic's next fight with Jerome Le Banner has been rescheduled to DREAM.5, July 21, 2008. The rescheduling is due to Mirko sustaining a minor leg injury.
My question is why not let Fedor fight in his sambo league (one of the deal breakers in the contract negotiations with Fedor) if they are going to let Crocop fight in Japan?