The riot shield of the 20th and 21st century was a clear plastic deterrent used to protect police officers while working to contain crowds and riot situations. The shield was plastic, and worked well enough. A shield is a shield, and as long as no one in the crowd had a heavy calibre weapon everything was pretty much fine. But the advent of the Cosmic era changed the game. Energy weapons became feasible, and a plastic ballistic shield did absolutely nothing to stop a coherent laser beam and if hit with a plasma round had a nasty habit of quickly turning into a splatter of molten hot or burning plastic goo.
The new Riot Shield was created, a composite structure that mixed ballistic protection with energy dissipating materials. The transparency was lost, and the shield roughly doubled in weight.
Megacorporations and corporations vie with governments and government agencies, and the front line of that battle is advertising, and branding. The private security companies, like Lone Star or Knight Security struck first, fielding branded shields. The Lone Star shield was a matte blue with an asymmetrical set white star and the corporation name emblazoned on it. This quickly became the symbol of Law Enforcement in the Atlantic Federation, gaining ground over the previously accepted police uniform and star badge.
Now every security company that has riot gear, has a branded shield. Agents that are subcontracted to other non-security corporations have multiple branded shields, such as the dual Lone Star/Rocketdyne shields used by security troops that cover the Rocketdyne Megacorp factories and HQ in the Houston Space Megaplex.
The shield is a commercially available good, and can find its way into various hands. It is not uncommon in the Cosmic Era, an era of intelligent robots and hypertechnology for rebels and gangs to run around carrying a tool thousands of years old. Such rebels will usually decorate their shields in a fashion that orcs would approve of. Such imagery is quick to find it's way to news feeds around the world.
This submission has two ideas that I want to express about the Cosmic Era: corporatism and the acceptance of violence. The corporations and megacorporations are fighting wars between themselves over control of the global economy, and advertising is their first weapon. Shields appear on news feeds and data streams, they were unexploited advertising territory. The Paramilitary and security companies used a common tool and made it a billboard for their brand. Military units sometimes use heavier versions of these shields, but these are unbranded objects, and only used in certain circumstances, such as defence in rough terrain, or by heavy infantry or power armor units facing other similar infantry units. The acceptance of violence is just another part of the Cosmic era, and it's Escalation Scale. Weapons are common, hold overs from the Second Dark age, and then combining with rapidly advancing technology and the emergence of things like parapsychic abilities that turn hands and fists into weapons on par with most hand held weapons. Security personnel are not rent-a-cops like the sort who patrol Malls, or the Student Resource Officers (cops in schools), they are soldiers, clad in body armor and carrying serious weapons and things like shields. This is just part and parcel in a world where the next person to start a problem could be carrying a plasma pistol, could be a Ryu type parapsychic martial artist, or could be an android largely immune to intimidation.
Additional Ideas (1)
There are three basic versions of the Riot Shield: civilian, commercial, and military.
The Civilian Riot Shield is the sort that is legally obtainable through military surplus stores and catalogs. It is a standard ballistic shield but lacks the thermo-ablative properties of the higher grade shields and it looks more impressive than it actually is. In certain areas, the shields are registered like firearms would be, since someone willing to buy one of these items is more than likely to have firearms as well.
Commercial riot shields have the full array of ballistic and ablative protections, as well as having a special high impact resistant resin coating to protect the advertising and logos presented on the shield. You might not survive that grenade blast, but your Lone Star shield will. It is available in matte, satin, and full gloss finish.
Military Riot shields are fitting with larger grips so they can be easily used by both basic infantry and by heavy infantry in hardsuits. They have the full protection value but lack the durable but expensive resin coat.