One's legal status was the position one occupied according to law.
In 2365, Jean-Luc Picard vowed that Data's legal status - whether he was a person or property - would be settled in a hearing before Phillipa Louvois once and for all. Louvois later declared the purpose of the hearing at its commencement, noting that the Judge Advocate General had declared Data property, but that the finding was being challenged. (TNG: "The Measure Of A Man")
In 2369, Data reminded Picard of his having fought on the android's behalf and his gratitude that Picard had done so, adding that the exocomps had no advocate to fight for their status as living beings. (TNG: "The Quality of Life")