Board has held that the execution of separate agreements that would permit either the union or the employer to escape the binding effect of an agreement resulting from group bargaining is a refusal to bargain and an unfair labor practice on the part of both the union and any employer executing such an agreement. The remaining members of the unit thus can insist that parties remain subject to unit negotiations in accordance with their original understanding. Bonanno, — U.S. at —, 102 S.Ct. at 726 (citations omitted). But the propriety of an employer’s withdrawal from its unit should not be divorced from any considerations of the agreement entered into by the employer and the unit before the commencement of negotiations. Compare Teamsters Local No. 378, 243 N.L.R.B. 1086, 1087 n.5 (1979) (<HOLDING>) with Authorized Air Conditioning Co. v. NLRB,
holding venue provision of federal employers liability act nonwaivable holding that there is a duty to check articles of incorporation of defunct corporation for identity and address of directors holding antiwaiver provision of securities laws does not prevent enforcement of contract provision choosing english forum recognizing that most small articles are not produced as individual or separate products of the loom but for economy of manufacture are first woven in the piece  and stating that where such articles are imported in the piece and nothing remains to be done except to cut them apart they shall be treated for dutiable purposes as if already cut apart and assessed according to their individual character or identity but only where the character or identity of the individual articles is fixed with certainty and where the woven piece in its entirety is not commercially capable of any other use holding that legality of employers withdrawal does not turn on provision of association bylaws or articles of incorporation