18. Persons on whom settlements and awards are binding.- 2[
A settlement arrived at by agreement between the employer and workman otherwise than in the course of conciliation proceeding shall be binding on the parties to the agreement.
3[ Subject to the provisions of sub- section (3), an arbitration award] which has become enforceable shall be binding on the parties to the agreement who referred the dispute to arbitration.]
4[ ] A settlement arrived at in the course of conciliation proceedings under this Act 5[ or an arbitration award in a case where a notification has been issued under sub- section (3A) of section 10A] or 6[ an award 7[ of a Labour Court, Tribunal or National Tribunal] which has become enforceable] shall be binding on--
all parties to the industrial dispute;
all other parties summoned to appear in the proceedings as parties to the dispute, unless the Board, 5[ arbitrator,] 8[ Labour Court, Tribunal or National Tribunal], as the case may be, records the opinion that they were so summoned without proper cause;
where a party referred to in clause (a) or clause (b) is an employer, his heirs, successors or assigns in respect of the establishment to which the dispute relates;
where a party referred to in clause (a) or clause (b) is composed of workmen, all persons who were employed in the establishment or part of the establishment, as the case may be, to which the dispute relates on the date of the dispute and all persons who subsequently become employed in that establishment or part.