First of all, this isn't Dungeons & Dragons and Paladins are not required to be "Lawful Good." Furthermore, "Orderly" is not really the same as "Lawful."

Secondly, if the character in question is actually a Maran, or on that path, their primary focus is to destroy Darkness. In attempting to achieve that goal, a given character may take the tack that almost anything goes in pursuit of that end-result. If this means that a cityguard must die, so be it.

Obviously this isn't how a Baer Pally would approach things, but who's to say that this was one of hers?

The good news is that there's something in the game to balance out the single-mindedness of the Maran. They're called Acolytes.

If you think a given Maran is too bloodthirsty or, worse, in danger of becoming like those he seeks to destroy, take it up with an Acolyte and hopefully they'll steer the (possibly) straying Knight back to the "right" path.

Also, it was my take (with my Maran, who was N/G) that there was really nothing wrong with being warranted, but I'd generally turn myself into the next Lightwalking Magistrate I saw.

And, dude, deal with this stuff in game.