No, a 501c3 IS legally obligated to provide you with their form 1024 (application) and their last three 990's (if not available online) if you ask for it. If you send a registered letter - even to a PO Box - they have 30 calendar days to get that information sent to you. They can ask for you to pay for the printing and mailing charges. If they don't provide it when requested, they can be subjected to heavy fines. It's also easy to find out if a group is a 501c3 or not. You can look it up on the IRS site.