Using the order, the Coxes were able to get a Utah judge to change the home's title about two weeks ago, Downing said.
Susan Powell was last seen at the home on Dec. 6, 2009. Josh Powell, her husband, moved with their two young sons to Washington about a month later and subsequently rented out the home.
Josh Powell killed himself and his sons Charlie, 7, and Braden, 5, on Feb. 5 by setting fire to a rented home in Graham, Wash.
At the time of Powell's death, the Utah home was still listed in both Josh and Susan Powell's names.
Downing said a Washington judge also named the Coxes personal administrators for their grandsons' estates. Josh Powell had insurance policies in his sons' names worth $500,000, as well as $1 million policies in both his and his missing wife's names. Those policies are now the subject of a court action between Josh Powell's siblings and mother and the Coxes.
He said Josh Powell's family received notice of the Coxes' appointment as administrators for their daughter's estate.
In that role, the Coxes have a duty to marshal "any and all" properties to which Susan Powell would be entitled and manage and protect it "until she's found" or officially declared dead. Downing said the Coxes now are responsible for ensuring the mortgage is being paid and rent collected on the 3-bedroom, 2-bathroom Utah home.
Josh Powell had set up a "rent-to-own" contract with the current occupants of the home, valued at $138,000, but "he'd made promises about things he was going to do in the home that he had not done," Downing said. The Coxes plan to make those repairs and upgrades as their finances allow and proceed with the home's sale.
Nate Carlisle contributed to this report.