Do you "Require" or "Highly Recommend" that leaders come to your Leadership Development Programs?

I'm interested in finding out if large-scale organizations that provide leadership development programs either “require” or “highly recommend” their offerings for leaders. I’m interested in best-practice recommendations. I’m of the mind-set that I want leaders to participate in leadership programs because it is of value vs. being told to come. Yet, I understand that some organizations make it a requirement. If so, are there consequences for not attending a program and how is it monitored? I welcome input. Thank you!