My husband's ex asked him to pay for summer camp $2880 which is 37% of his pro rata share.but when my husband asked her proof of payment, she said is not going to give him any.is this fraud?

No one 'made him pay.'
Not getting immediately proof he paid is just foolish on his part.
He should have paid the camp directly even if it was a fraction.
Fraud would be if he could prove that the money wasn't used for what it was intended. Fraud between exes of this sort is commonly called deceit more than fraud.
He can try Small Claims court.

Actually I forgot to include that she took him to court because of that and the judge made him pay without even asking proof of payment

My husband's ex is working as a counselor in a summer camp.One benefits of the camp when you work there is one child free.Now,she asked him to pay for the camp and my husband refused because she can't provide proof of payment and she said he will never give him any.then,she took I'm to court and the judge just let him pay without even asking proof of payment!( what a judge is that? Does he got brain at all?)what is the best thing to do to sop this BS.

Have a better lawyer when you go to court, obviously the person who had to pay without her providing proof did not file the right and correct motions in court, or proper ( in legal manner) object to the things the ex was filing.

No it is not fraud, at this point, if she testified in court that she paidi this, then it would be lying under oath.

But the time to prove it was fraud was in the court case

*** please stop asking the same or similar questions over, keep this in one question or I will have to start deleting them.

No its not fraud. Why didn't he just contact the camp and ask the cost? And yes, he probably blew it by not asking the judge to force her to provide proof.

No its not fraud. Why didn't he just contact the camp and ask the cost? And yes, he probably blew it by not asking the judge to force her to provide proof.
He tried but the judge never let him talk.

Was he represented by counsel?

Was he represented by counsel?

No.he can't afford to pay one so he did by himself.

No.he can't afford to pay one so he did by himself.

So let me get this straight. Instead of paying for an attorney he wound up paying almost $3K for summer camp! And you are trying to tell me he can't afford an attorney? He can't afford NOT to have an attorney.