Can someone offer me advice...please?

I have a situation and I need advice. I offered some friends a place to stay when they lost their home. I did not ask them to pay rent, but to split the food bill with us. They said they would then moved out a month later and never paid us, they left some of their belongings at my home. I contacted them about their belongings and said they could pick them up but I wanted the money they owed us. They said it was illegal for me to keep the items till they paid us. Is this true?
Please know that the amount they owe is less than $50 and the item value is less than $50.
I would like to return their items, but I don't feel that they will repay the money.
I'd like stay within the law and I need advice.
I've never been in this situation and I'd like to resolve this in the kindest way possible because they are friends, but I don't want to be taken advantage of and loose money.
Can someone please offer me some advice?

Thank you in advance!

They are holding on to your money so why can't you hold on to their property? Let them take you to court and counter sue for your money. If they don't take you to court it's a wash

Count your blessings. When you let them move their clothes into your house, that house became their kingdom. They could have stayed there for free until you sued them for unlawful detainer.
Give 'em there stuff. It's only fifty bucks. A lesson learned.