The cases about secular enforcement of Muslim dowry-on-divorce agreements (see below) remind me of a broader thought I had offered before about Islamic agreements and American law: Those agreements should be treated the same as other agreements, without any attempt to specially nanny-state the parties.
If American law provides for certain constraints on contract enforcement generally -- e.g., you can't contract to have your hand cut off, certain prenuptial agreements are unenforceable, contracts entered into by minors are unenforceable unless properly ratified when the minor becomes an adult, parties can't contract away the rights of nonparties, such as the parties' future children, etc. -- those same constraints should apply to Islamic agreements. That should be true of agreements to arbitrate pursuant to certain rules, agreements to pay money in the event of a divorce, or whatever else. But if American law allows people freedom of contract, even when the people are young, foolish, socially pressured, and the like, Muslim people are as entitled as other people to such freedom (with the burdens that freedom often yields).
Sometimes the enforcement of the agreements might hurt Muslim women, who we think were wrongly pressured by family, community, or religion into waiving important rights. Sometimes it might help Muslim women, as with the enforcement of promises of a certain payment on divorce. But that, I think, shouldn't much matter, because the more important point is that Muslims, women, and Muslim women should be no more and no less entitled to freedom of contract than the rest of us.
If they feel undue pressure, the harsh but proper remedy is for them to leave the source of the pressure, again, whether family, community, or religion. Of course the law should protect them as best it can against unlawful (for instance, violent) retaliation for the departure; but that should be the extent of it. This "leave and take the social consequences, or stay and live with the contracts you make" is the remedy American law offers to the Amish, Hasids, Mormons, Catholics, Baptists, or anyone else, religious or not, who are dissatisfied with what their families, communities, or religions demand of them. It should be no different for Muslims.