The Collaborative International Dictionary of English v.0.48:

Falcidian \Fal*cid"i*an\, a. [L. Falcidius.]
   Of or pertaining to Publius Falcidius, a Roman tribune.
   [1913 Webster]

   Falcidian law (Civil Law), a law by which a testator was
      obliged to leave at least a fourth of his estate to the
      heir. --Burrill.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

FALCIDIAN LAW, civil law, plebiscitum. A statute or law enacted by the
people, made during the reign of Augustus, on the proposition of Falcidius,
who was a tribune in the year of Rome 714.
     2. Its principal provision gave power to fathers of families to
bequeath three-fourths of their property, but deprived them of the power to
give away the other fourth, which was to descend to the heir.
     3. The same rule, somewhat modified, has been adopted in Louisiana;
"donations inter vivos or mortis causal" says the Civil Code, art. 1480,
"cannot exceed two-thirds of the property of, the disposer, if he leaves at
his decease a legitimate child; one-half, if he leaves two children; and
one-third, if he leaves three, or a greater number."
     4. By the common law, the power of the father to give his property is
unlimited. He may bequeath it to his children equally, to, one in preference
to another, or to a stranger, in exclusion of the whole of them. Over his
real estate, his wife has a right of dower, or a similar right given to her
by act of assembly, in, perhaps, all the states.