The Collaborative International Dictionary of English v.0.48:
Pais \Pa`is\ (p[.a]`[-e]"), n. [OF. pu["i]s, F. pays, country.]
(O. E. Law)
The country; the people of the neighborhood.
Note: A trial per pais is a trial by the country, that is, by
a jury; and matter in pais is matter triable by the
country, or jury.
Bouvier's Law Dictionary, Revised 6th Ed (1856):
PAIS, or PAYS. A French word signifying country. In law, matter in pais is
matter of fact in opposition to matter of record: a trial per pais, is a
trial by the country, that is, by a jury.