The checks are the legislatures that give them laws to enforce, and the courts/judges that constantly choose to allow their lack of education of the law they're enforcing. Ignorance of the law isn't an excuse, unless you're a cop. It's the judicial system's fault. This is one area where I heavily dislike the traditionally conservative brand of politics. Consistently pro-cop rulings, even in shady situations, under "qualified immunity." That crap needs to be abolished, or God save us all.
Luckily the pendulum seems to be swinging, finally. Ending qualified immunity used to be a left/liberal policy, but now I'm seeing more right-leaning people advocating for it. Maybe it'll only be a matter of time before we can have pro-2A rulings and pro-citizen/anti-cop-hypocrisy rulings. Just gotta get the boomers and old borderline millenials out of the courts first.