Prospective tenant wants reason for declining them.

[Sam Abe]

I was considering a tenant for my rental and asked them to fill an online credit check with MySmartMove. The system recommended one of the occupants as DECLINE and so I declined their application and now they want written reason. How do i handle this as I don't  want to get in trouble and genuinely declined based on the systems recommendation though Credit score was ok.

They sent email saying: We request our requisite copies of our Transunion credit checks, and written reason for being declined as legally required.