California is the most famous example, with checkpoints at all road entryways to check for and control entrance of raw produce. Oregon likewise has checkpoints to check incoming watercraft for waterborne pests.
I'm sure truckers can also tell you all about the various trailer regulations that vary between states, not to mention the weigh stations most states have at border crossings.
As someone who has crossed that border many times in Tahoe, enforcement a) relies on the honesty from the people in the car b) runs seemingly randomly (ie more than half the time there is no checkpoint c) even when running enforcement is applied selectively based on whether you have California plates or not.
I think OP is probably talking about the practical effect of success of trying to control state borders effectively vs what you see which may be mostly for show / best effort. Of course you may be replying to “mass scale” smuggling vs what independent people may try to smuggle.
But I guess the level of scrutiny is way laxer than that at international borders.
My point was how effective would be a policy like the one instituted by Oregon be, when the state can't effectively control the flow of drugs? Wouldn't any progress be offset by "leaky" borders and the free flow of people?
Slow down for the inspection point. Approach the officers. Mostly they just waved me through without checking anything except maybe my license plate with a smart camera. Once they asked me if I had any fruit or agricultural products. One time I answered yes and handed over some apples and said “thank you” and was waved through.
It is nothing at all like a “border”.