Answered your question already. Answer mine. :)
You are conflating them and destroying that distinction when you use the example of the the federal government imposing a tariff or embargo on foreign goods with them regulating the movement of goods between the states.
Please explain why you want to destroy that distinction, and subvert the intent of the clause.
As for your question, I don't know what WA's plan is to prevent that, nor can I find anything that dictates that they need one. The architecture of the republic laid out in the Constitution makes each state a sovereign government, able to exercise within it's own borders any power that was not transferred to the national government. With power comes responsibility, and the resonsibility for enforcing those laws falls on the state that enacted them. A state may enter into agreements with neighboring states to cooperate in enforcement of those laws, but they are not obligated to commit resources to enforcing the laws of a neighboring state.
If the state of Washington wants to permit the posession of marijuana, an the state of Oregon does not, then it is the responsibility of the state of Oregon to enforce that restriction on it's citizens.
If enough states what to prohibit the posession of marijuana and grant the federal government the authority to enforce that prohibition they can propose and ratify an amendment to that effect, and then the federal government will be legitimately authorized to exercise that power. The is the purpose of the process of amendment. Calling it an exercise in "regulating commerce" is a corrpution of the intent of the Commerce Clause, and frankly it's bullshit, and dangerous bullshit at that.