In the week since announcing it was banning Los Angeles Clippers owner Donald Sterling for life, with the hopes of getting approval from the league's owners to force him to sell the team, little has been known of the NBA's exact legal strategy.

While the league's constitution, publicly revealed for the first time by the league last Tuesday, made it clear that grounds exist to remove an owner if that owner "fail(s) or refuse(s) to fulfill its contractual obligations to the Association," it remained unclear what contracts Sterling might have violated when he made his racist statements in a private conversation with his mistress V. Stiviano that was later published by TMZ.

But sources with knowledge of the league's strategy say there are, in fact, actual contracts that it will maintain Sterling violated should he choose to fight the league's desire to force him to sell the team if the league can get the required 75 percent of owners to agree to make the move.

One of those documents, which Sterling signed when he first bought the Clippers in 1981, and signed various amended versions since, states that an owner will not take any position or action that will materially and adversely affect a team or the league. Owners also sign morals clauses, which state that they will be upheld to the highest standard of ethical and moral behavior.

When morals clauses are enacted and result in termination of agreements, including endorsement deals, the courts are often charged with interpreting who was right, but sources with knowledge of the NBA's legal strategy believe that they have enough to force Sterling to sell.