Holding that the NLRB has the authority to interpret CBAs in the first instance where its interpretation is for the purpose of “enforc[ing] a statutory right which Congress considered necessary to allow labor and management to get on with the process of reaching fair terms and conditions of employment”
Concluding that since "the Board is not required to observe automatically all the rules of evidence governing the trial of cases in court," it was entitled to create a new evidentiary rule