The laboratory has a DEA-license to handle controlled substances. You are not breaking the law by sending in a pill, although you must follow the instructions exactly as described at the bottom of this page, and send in the pill anonymously. This program is for US residents only. The lab cannot accept pills from foreign countries because customs does not allow controlled substances to enter the US, even if the package is going to a DEA-certified lab.
All pills sold as 'ecstasy' are fine.
However, we especially encourage you to send in pills that you think may be fake or adulterated. These are the pills we particularly want to identify. Also, we encourage you to send in pills that produce no effect at all. It probbaly does not contain anything dangerous. This depends on how busy the lab is.