We're still expecting paladins to live up to social mores in a broken society? When the laws of man are built to carry out evil, they lose to the laws of your God or gods. IMO, that's the only way to make a paladin playable in any sort of political setting.
When the rulers are evil and oppressive, they're usually using social rules to their advantage. In medieval and literary courtly societies, this usually involves misapplying the Divine Right of Kings and arranging situations so that the biggest, baddest guy in armor is on your side and will beat the snot out of anyone who looks at you crosswise. This can be in battle, as part of a Duel/Challenge, or even the deciding factor in a court of law. Trial by arms was around for a while, after all, and often became part of a more complex legal system.
Now, let's say that our paladin is the mightiest knight on life, and a member of the court, but has been entirely unsuccessful in stopping the oppressive urges of the rulers. He's even tougher than their champion, but they're smarter than he is, so they outmaneuver him socially and legally so that they can unleash their pit bull knight and lackeys on others, and he never gets the chance to lawfully stand up for right, at least not on major issues. he might have had some minor victories early, before they started go out of their way to control him from the beginning. He's being tied up in the rules and made ineffectual.
In my mind, that's a hellish environment in which to be a paladin. To my way of thinking about paladins, good laws bring prosperity, happiness, and even godliness to all the people. Just laws do the best job of doing the greatest good for the greatest number. Having bad law used as a weapon against him would be maddening.
Our boy, though not overwhelmingly sharp in a political sense, is a lucky guy, and stumbles upon proof that a minor noble has been up to some shenanigans. Turns out he's running a night guild on the side, and using what he learns as part of his duties in court to make unfairly levied tax monies disappear and migrate back out to the poor. He's even sharp enough to make it look like typical guild or manor inefficiency when it isn't out-and-out brigands and bandits. So, the money STAYS with the poor and destitute who need it, because no one's turning out the hounds to find it. Also, his "beggars," burglars, and assorted other personnel are actually the only thing keeping the streets safe at night from the truly contemptible "city watch" that has unsavory habits vis a vis the poor or any young women who make the mistake of being out-of-doors at night or alone.
Now, these cats ARE burglars, footpads, etc.... but not only are they being organized to hit targets who are profiting by abuse of the system, but they're protecting the weak and helpless while they do it. I imagine our paladin takes a few deep breaths at this point, but ultimately, while the guild is breaking the laws of man, they're the only thing in the city serving the laws of God right now, something he has been entirely unsuccessful at himself of late.
So, we have a mighty knight who could make a serious difference if he could be unleashed in the proper venues, and a smart man who may be canny enough to make sure he is properly unleashed. Some sort of trial will naturally come up, and the paladin will try to intercede and start making a mess of things. Possibly even overextend himself and risk losing his own position to legal technicalities. The guild leader will have an attack of conscience and step in to outmaneuver the legal chicanery and get our paladin in place to bring about the rightful conclusion. Of course, the minute our guild leader visibly steps up to the plate, he becomes a threat that the corrupt rulers want to eliminate. They've been laughing behind their hands at Galahad over there for a few years. It's been great to watch his face fall every time they shut him down, but now the punk has found himself a brain by proxy. And he's a nobody! Not even a member of the peerage, he's been quiet and unassuming and now he steps up and makes them look like fools! So, now the paladin has to place himself in the guild leader's back pocket, becoming his bodyguard, for all intents and purposes, because if he loses this guy, any chance he has of making a difference goes out the window.
Being a paladin, I imagine he strikes a bargain with the guild leader: I'm your bodyguard and champion. I will protect you with my life, but you must continue to fight for righteous causes at court. And your guild may continue to operate, but I'm going to be with you at every meeting, and I want the ability to remove people from the organization. (Go go rousing speeches to truly be the Night Guardians of our fair city- gots to love that high Charisma score. No better way to get people to BE good than to convince them they ARE good). Of course, the increased attention they're going to get by being visible at court is going to run HUGE risks for the guild, but the guild leader sees the benefits in being able to take action in court. They might make REAL progress instead of this rear guard stuff. Naturally, he'll insist on getting the paladin in on guild operations, as well. If the paladin is in it up to his elbows, he can't pull the plug as easily if he has an attack of conscience about the vagaries of the situation. Naturally, he'd only send the paladin on the squeakiest clean missions with the real romantic types (read: CG) who really DO think of themselves as righteous revolutionaries and guardians of the people.
Of course, if you use Detect Evil (or your paladin is simply astute about such things), there WILL be evil people in the guild that he will root out. He'll argue with the guild leader about it. But, being a paladin, he'll be adamant on this issue, and the guild leader will sigh and go ahead and remove them publicly. Naturally, he will then go behind the paladin's back and have them very quietly killed and disappeared before they can go to the authorities. A regrettable action, but necessary to protect the guild's ability to do good, and what the paladin doesn't know won't hurt him. (And if anyone tells he this would make the guild leader evil.... Killing an evil person to protect a good organization is evil, but genocide perpetrated on kobolds, goblins, and orcs is perfectly good? Or at least allowed, I suppose. Not buying it.)
Assuredly, there will be conversations about what to do with this guild once rightful rule is restored that will likely strain the relationship between the paladin and the guild master. Additionally, causes will come up at court that, while righteous, cannot be won, and the paladin and guild leader will clash on what do to. The paladin will want to risk it, because it is right, but the pragmatic guild leader will point out that some kinds of losses would be TOO risky to their precarious position. And if they do succeed in restoring righteous law (or simply hold on until King Richard shows up), the paladin will seek to disband the guild and find them all respectable trades. But when you're fighting out-and-out social evil, you have to use the tools at hand. Being a paladin, he'll not simply use that imperfect tool, but temper and even polish it as he goes.