The reality is that tear gas is not an effective riot control tool. It works fine against spontaneous mobs of sports fans after their team loses, but it's not especially effective against prepared insurrectionists.
The last time the US faced this level of organized political resistance against lawful federal authority, the Army and National Guard routinely used fixed bayonets to control segregationist protesters. The same technique would work today, but with modern rifles being significantly shorter and hence being less effective bayonet platforms, a dedicated spear might be the better option.
Such weapons, employed in a close-order formation, would be much less lethal than they might seem at first blush. Historical data from 18th and 19th century conflicts shows that, even in battles where bayonet charges happened, there was still an extremely low rate of actual bayonet casualties. Even trained and disciplined soldiers will break and rout rather than let themselves be stabbed with bayonets (or, presumably, spears).