I reviewed the NBA Constitution quickly this morning. It was put online by the NBA. Here are a few of my quick thoughts:
1. Article 13 does not permit the Board of Governors to terminate an Owner's membership unless the Owner is accused of willfully violating the Constitution, By-laws, or "doing any of the following", which then lists certain other specified matters that do not pertain to his racist remarks. So I see no grounds here at all, and if they were to try to do so, Sterling would have a very good defense.
2. Article 24 grants the Commissioner broad authority and duties to "protect... the integrity of the game of professional basketball and preserving public confidence on the League." This grants the Commissioner authority to investigate, try, and decide any matter "that may adversely affect the Association or its Members." Clause (l) of this Article, for example, gives the Commissioner the right to impose a penalty not to exceed $2,500,000, "wherever there is a rule for which no penalty is specifically fixed for violation thereof". The problem for the Commissioner here is that Article 35A, clause (c), which covers Owners, provides that "any person who ... makes .... any statement having .... an effect prejudicial or detrimental to the best interests of basketball or of the Association....shall be liable to a fine not exceeding $1,000,000".
My quick conclusion: I see no grounds for the NBA owners or Commissioner to force Sterling to sell the team for the racist statements that were made. I also think they probably fined him more than permitted under the Constitution, and that the fine will eventually be reduced to $1,000,000.
Bottom line: It will be very difficult for the League to force Sterling out, and that if they attempt to do so, we can expect a long, protracted fight.