"Developed stored procedures for an international banking organization. During this project I used PL/SQL and was exposed to domain knowledge in low latency transaction processing. Familiar with ACH protocols and international wire transfers."

"Designed, developed and maintained a relational database servicing 3,000 client machines processing 46,000 transactions per day with high throughput and low latency for an entertainment company based out of Nevada."

If I saw those on your resume, I wouldn't even make the connection to gambling or illegal activity, and even if I did suspect it, who cares?

"This is going on your PERMANENT RECORD!"

Just emphasize your technology role and put some positive spin on the industry/sector, if its actually illegal then cite confidentiality agreements that prevent you from disclosing the actual company and flip the conversation back on the role and skill set.