As to your first question, about who owns the Dragonlance intellectual property, that appears to have always been Wizards of the Coast. According to a Q&A on the website of Tracy Hickman, the co-author of the core trilogy:
We were not unique in this: everyone working at the company at the
time was under similar constrictions. We were being paid to create and
play games and it was a condition of that employment that we hand over
our rights to our creations. Those rights were sold as part of the
purchase of TSR, Inc. by Wizards of the Coast and then subsequently
owned by Hasbro when they acquired the company as a subsidiary.
As to your second question, regarding a court battle between Weis and WotC, I was unable to find any mention of such a case. The closest I found was the following paragraph from this article on Dragonlance on WotC's D&D website:
Wizards continued to publish Dragonlance novels throughout the ‘00s, but they opted not to release additional gaming books. Instead, they licensed those rights out to Weis’s own company, Margaret Weis Productions (originally: Sovereign Press). The result was the most prolific period of Dragonlance publication since the early ‘90s.
According to this archived post by Jamie Chambers on Dragonlance.com from January 31, 2008, those licensing rights reverted to Wizards of the Coast in 2008.
Update: As V2Blast points out in a comment below, it does appear that Hickman and Weis sued Wizards of the Coast for breach of contract by denying to give contractually obligated feedback. The filing can be read on document cloud and scribd. In December of 2020, they dismissed their lawsuit. In January of 2021, a new trilogy of classic Dragonlance novels was announced.