Contract printing for a client selling licensed images on products - how do I protect myself?

Hi, my company digitally prints promotional merchandise. Recently I was contacted by a company who wants us to contract-print for them. They will be selling licensed NFL, NBA, NHL, etc. images on iphone covers to major retailers nation-wide. Our initial order is for 6,000 units, with more on the way - and I'm concerned about my company's protection against potential lawsuits from printing these licensed images. I know I need a copy of the licenses showing his legal ability to print these images - but not sure exactly what should be included in the copy I receive. I'm also wondering what other agreements need to be in place in order to protect myself should the licensee bring forth a lawsuit against this company in the future. Even if not a suit for printing the images themselves, but perhaps for not printing them correctly or as-approved by the licensee. I also won't know when or if he looses his license, which means I'd be printing these images for him illegally.