Duke, here's what I could tell you since I studied law a bit some time back.
If WU wants to take you to court, they could demand that you release the name and address of the person you're sending it to. They could also intimidate you so much so that you'll be giving them the site where you got the info from. But other than that, they could do nothing to you.
Since WU already have the Name and Address of the person you're sending the money to, there's no way they would want that again. They most probably think that you're actually sending this money to fund some terrorist group or something like that so that's why they are demanding that you sign papers and etc.
As for Money Laundering, you don't really have to worry much about that either. $15K is chump change as compared to the real money launderers. They launder about $15M (at the least). If you need more information about money laundering and etc, please do visit
http://www.laundryman.u-net.com or
http://www.imolin.org/imolin/index.html
Other than that, don't worry about the letters or emails or etc that they send you. But if you really wanna feel secure, just consult your local Lawyer and he/she will be able to advice you accordingly.
Don't let methods of intimidation fool you.
Just a side track story. A friend of mine actually registered a domain name which has the word "dell" in it. After 1 month, she received a Fedex from DELL's Lawyer from the USA (she lives in Malaysia) and it demanded that she gave up the right to the domain and gave it to DELL. She was so intimidated by the lawyer letter that she agreed.
After knowing me, asking about this and etc. I brought her to my friend who is a lawyer in Malaysia and she found out later that she need not do that. No Lawyer in another country has the right to prosecute you unless you've done something wrong in the Original Country that the prosecutor resides.
So, unless you did do something wrong in the Phillipines and/or did break some law or something, WU could only prosecute you by getting a Phillipine Lawyer and not try to pull a hoax or something by getting a US Lawyer to prosecute you. If they do try it, your country will stand up for you. Trust me, it's been seen and proven over time and time again
Hope this bit helps.