I don't think it's legal to walk across or stand in the middle of the road to begin with (anywhere except a crosswalk while the light is red).. but besides that, no, I don't think there should be special laws against it, because I think a little bit of economy/commerce/workforce/car-pollution-jamming is a good thing. The protests behind those road blockages are probably more important than the ability of the drivers to get where they want to go, and making it illegal is just authoritarianistically preserving the status quo.