The Dormant Commerce Clause is not found in the Constitution, however, it allows the US federal government to regulate commerce within the states, US territories, and international commerce. Therefore, When any state law contrasts with the Commerce Clause, the dormant commerce clause takes effect. Now in this situation, Puerto Rico is restrained from enforcing any laws concerning commerce, since it is still under "US territories, the control to exercise such is left to the US government. So, based on this facts, I will say YES the Puerto Rican law broke the dormant commerce clause. Puerto Rico as a US territory does not have the power to regulate the cement labels because this law concerns commerce.