Muslims living under Western Law

When you go through divorce, have you or would you expect to follow Islamic law on how to part ways?

Child alimony as a western provision is an Islamic concept that comes from when the Muslims conquered Andalusia. However, alimony past the Iddah is not in Islam. The Mehr of course is our mechanism.

I know a few couples who have divorced, and western courts split assets and provided for years of alimony etc.

To the people who do this or support this, how do you justify this? Also, how do you expect a Muslim man in the West to take this risk?