Courts are reluctant to overrule other courts. Michael was Terri's official husband.
We need to take a hard look at these laws. Terri's parents and siblings were (IMO) obviously better qualified for that role.
As far as the guardian thing, the Schindler attorneys petitioned Judge Greer first (and, I think, the judge prior to Greer). Greer denied the petitions and didn't rule timely on others. The appeals courts agreed with the procedure -- Greer had a right to deny the petition (without saying whether or not he should have denied the petition).
The same thing happened when they asked Greer to recuse himself several times. He said no. Appeals courts said he had a right to say no. No one else looked at the facts as to whether or not there were grounds to remove MS as guardian or Greer as judge.