If you're talking about more than one justice, the correct plural is justices. The singular possessive is "justice's"; the plural possessive is "justices'."
The plural of justice is justices.
The plural of justice of the peace is justices of the peace.
The plural form of chief justice is chief justices.
Justices.
Lord justices.
Coaster's is singular possessive. The plural is coasters, the plural possessive is coasters'.
The correct form is "its" for the possessive form in the plural. "Its" is used for both the singular and plural possessive forms, without an apostrophe.
The plural is briefs. The plural possessive is briefs'.
The plural is lads. The plural possessive is lads'.
The plural is trollies. The plural possessive is trollies'.
The plural is stations. The plural possessive is stations'.
The plural is relatives. The plural possessive is relatives'.