Holding that courts must not "substitute [their] judgment for those of the Board with respect to the issues that Congress intended the Board should resolve"
Holding review of the Board's decision to apply a new rule of law retrospectively is deferential and that the Board's ruling will be disturbed only if it wreaks manifest injustice
In Wehr we observed: "As Fibreboard and First National Maintenance make clear, a decision to subcontract is not necessarily subject to mandatory collective bargaining; whether such bargaining is mandatory can only be answered by looking to the particular facts presented in the individual case."
Finding leading questions appropriate under similar statutory provision because "[b]y virtue of [former employee's] status as the proprietor of one of the respondent firms as well as his former official position within [the Defendant] Association, his interests and sympathies were clearly aligned with those of the other respondent"