Impugned legislation:  federal Industrial Disputes Investigation Act of 1907.

Viscount Haldane wrote the decision of the JCPC.  (You can guess the result.)  He wrote that the subject-matter of the legislation, labour legislation, clearly falls under s. 92(13).

Keep in mind that this case concerned a municipal transportation agency -- clearly an industry falling under provincial jurisdiction.

After determining that the subject matter fell under 92(13), Haldane then needed to ask whether it also fell under POGG, the federal crim power, or the federal Trade and Commerce power.   His answer was no.  The federal POGG power can be used as a residual power, or emergency power.  The "national concern" branch of POGG seemed to have disappeared, for Haldane.  Becauase the subject-matter falls under 92(13), the residual power is not relevant.  And there's no emergency.

Haldane tries to reconcile this decision with Russell v. Queen.  Was there an emergency concerning drinking in 1882?  Haldane writes that  the “…evil of intemperance [was] one so great” that parliament intervened to “protect the nation from disaster” back in 1882!