Protesters, apparently in Ohio, stand up for the right to hang temporary and attended freedom-of-speech protest signs on overpass fences, which are removed after the protest. Putting signs on the fence can greatly enhance the effectiveness of a protest. The police in various states frequently try to bully protesters into not hanging signs. This sometimes seems to be instigated by complaints from Department of Transportation workers, who are often unionized by the red-infiltrated, progressive union, Service Employees International Union (SEIU), one of Obama biggest contributors and source of campaign workers.
There are laws against hanging signs for advertisement and directional signs on the Overpass fences, but not specifically for temporary freedom-of-speech protest signs. Petty state and local laws cannot overrule the Bill of Rights. Police never seem to write a ticket anywhere in the country for hanging a protest sign on the overpass fence, which is evidence they they do not believe it will hold up in court. They usually try to trump up another more easily defended charge, such as creating a hazardous condition and failure to disperse, which depends only on their own judgement.
The primary role of the police is not to protect your constitutional rights, but to maintain public order within the law, as they see it. They are sometimes influenced also by those with a political agenda (such as the SEIU). They tend to err on the side of public order and see these protests as having the potential to become disorderly. So they also naturally have the inclination to try to inhibit them. Protesters should question the police and push back a little, as these are doing, and not just accept everything the police tell them as the gospel truth.
This clip is a little long (30 minutes).