Sure, everyone needs to do their part. But people hear about the pacific garbage patch, and they might think that laws like this will materially affect phenomena like this. But it's possible (I'm not an expert) that a law like this would have very little impact because the vast majority of the trash comes from different regions.
I find it's best to look at laws like this as social trends. Look at the way that same sex marriage or legal marijuana spreads through the united states. One or two progressive states adopt the policy, it gains steam, and soon it's the new norm nationwide.
I like to think that the same thing can happen on a global scale.
