Even harder is a squabble between your own child and your foster child.
I've only ever seen courtroom judges on TV and in films, where they usually come across as being stuffy and quirky. They don't seem to do any judging either. The jury does the judging. The judge gets to say things like "Sustained!" when one of the lawyers goes "Objection your honour!", which is a judgement on a detail of procedure. The business of deciding whether a person did something criminal is down to the jury. Then there are magistrates who decide who's right and wrong in civil cases. Small claims courts settle minor financial disputes.
Totally different are TV judges like Judge Judy and Jeremy Kyle who get to see the domestic war recreated on camera for our entertainment, and then do a bit of hammed up deliberating to get the studio audience cheering.
The professional judges have it easy by comparison to us. Every dispute in court hinges on laws which have been made so anyone can get the appropriate book down from the shelf and look it up.
Same with the police. When they get called in they have to decide if they think a law might have been broken. In the "good old days" we like to tell each other, a bobby would use his common sense and knowledge of human nature to suss what was going on, give someone a clip round the ear and cycle off for his tea.
Thankfully, squabbles between foster children are rare in my experience, but when they happen I find myself adjudicating like a cross between Judge Judy and one of those old-fashioned bobbies, except I can't cycle off for my tea, because most squabbles seem to break out around the house when I'm cooking tea.
The Crown versus the Missing Lego Piece
PC Plod (Me): "Acting on the noise coming from the living room, I proceeded in a westerly direction from the kitchen, having turned down the pasta, and moved the saucepan to the back of the cooker for safety reasons, your honour. On arriving at the scene I ascertained that Spongebob was ended and that a dispute had begun about a Lego figure who was missing one of the lightning horns off his helmet."
Judge Judy (Me): "Whose Lego is this one anyway, they all look alike to me."
My Child: "It's my Klanggo, God mum, you bought it with me, it's the one I got with gran's money."
Foster Child: "Yeah but the head isn't, it's the head off Zendip, who you gave me when we swapped it for my mum's Wi control"
My Child: "It's not, his head didn't fit when we tried, nor does the flamethrower, does it mum?"
Foster Child: "If my mum was here she'd tell you."
PC Plod: "At this point your honour, I inferred that Defendant A (My Child) hoped that if he made enough of a song and dance of it, the judge would be bound to agree with Defendant A on the basis of family. Defendant B (Foster Child) hoped that you were bound to agree with him because he's had more than his share of troubles already and that if you didn't it would be because you're biased."
Judge Judy: "Okay everyone here's what I'm gonna do. First I'm gonna do denial over bias, and make out it's unthinkable because if I allow anyone to think there is any bias going on we're all losers. Secondly I'm gonna make out that there's a chance I can solve this one AND come up with a solution everyone likes, even though that's never happened once in the entire human history of children's squabbles. So each of you go and look in your bedrooms for the lightning thing while I finish the pasta. And if you find it you can both have a lolly after tea."
Verdict: Judge Judy decided that in future all swapping is completely banned and that both parties received a lolly after tea for trying hard to find the missing lightning horn of Klanggo, which never turned up. Her joke that it must have fallen through a rip in the space/time curtain bombed. She resolved in future to get tea on the table to coincide with the Spongebob end credits.
Epilogue: As usual Judge Judy went back to the pasta full of self-doubt that she'd failed everyone; that both children were disappointed with the time honoured parent fudge verdict "You're both a bit right and both a bit wrong". She thanked her de-escalation training: you should calm tempers with distractions rather than confronting the problem, because the problem is usually deeper than the one you're presented with.
Mostly, she believes she is still one jump ahead of anyone thinking she has favourites. Which, being human, she has.