One of the aspects of Islamic family law that is often singled out as unfair is that female heirs seem to receive only half of what male heirs receive.
Muslims generally make two responses to this. First, this is not a general rule. There are any number of possible scenarios in which a female heir receives more than any male heir, or even than all male heirs combined. This one-half rule only applies when male and female heirs are of the same class (e.g., they are both children of the deceased or something similar). Moreover, the rule does not apply to every case when there are male and female heirs of the same class. For example, if the two heirs are the parents of the deceased, they receive the same share. An example of this type of argument can be seen in Position Paper on Islamic Inheritance.
Second, male heirs have a financial obligation that female heirs do not, namely, the male heirs are required to support the female heirs while female heirs are never required to support anybody. In other words, because the male heirs have extra financial needs, they get extra money to fulfill those needs. In practice, the male heir may have less money left after spending it on his dependents than the female heir has. In that case, it's the female heir who comes out ahead in the end, if the object is to have the largest amount of discretionary money through inheritance. An example of this type of argument can be seen in The Issue on Inheritance: The Unfair Treatment of Women?
A law journal article that I found this afternoon via Lexis takes these arguments one step further. The article is The Myth of Misogyny: A Reanalysis of Women's Inheritance in Islamic Law, 61 Alb. L. Rev. 511. The article is by Muslim lawyer Zainab Chaudhry. It does not seem to be freely available on the web.
Chaudhry provides a general background on Islamic jurisprudence and its sources, then introduces the reader to two concepts in Islamic legal theory: maqasid (intents or purposes of the law) and 'illah (legal cause). She then provides an overview of Islamic inheritance law and the rules of succession followed by some examples of female heirs inheriting the same as or more than male heirs. For instance, if a woman dies and leaves behind as heirs only a husband and a daughter, the husband and the daughter each receive one half of her property.
The article then returns to maqasid and 'illah, particularly 'illah. 'Illah is the legal cause of a ruling. It is the reason that the ruling exists. For those who are interested, here are three articles about 'illah: Methods Of Finding The Cause Of A Legal Injunction In Islamic Jurisprudence, Modes of Reasoning in Legal Cause, and How to Ascertain the 'Illah in the Islamic Legal System (PDF). You can also read Maqasid Al-Shari'ah: The Objectives Of Islamic Law.
Chaudhry applies the legal theory of 'illah to inheritance law, specifically to the cases where male and female heirs of the same class receive different shares. She writes:
Turning now to those two circumstances where a son and daughter, or a full brother and sister, are inheriting jointly, is the rationale for that Quranic injunction fixing a two to one ratio for such distribution based on gender? In other words, is the 'illah, the effective cause behind the injunction, gender?... ...If gender, as such, is the correctly identified 'illah in those cases, it must have a causal relationship with the injunction (the two to one ratio), and it must cause the same result (i.e., the same ratio) in every like circumstance. The result then should be the same in all cases where males and females of the same class are inheriting together from the decedent's estate, with the resulting injunction being a two to one distribution in all cases. As shown above, this two to one ratio is only apparent in the fixed allocations of two out of the four basic classes of relatives - sons and daughters and full brothers and sisters taking in their absence. Gender as such, is therefore considered to be an invalid 'illah and the claim that the sex-based inferiority of the female is the underlying rationale for the differences in the distribution cannot stand. To continue to believe so would violate the concept of ta'lil [finding the 'illah], one of the most fundamental pillars of Islamic legal theory.In this way, Chaudhry disposes of the idea that women in these cases inherit less because women are considered inferior. If women inherit less because women are inferior, women would always inherit less. They don't. Chaudhry then examines the obligation of male heirs to support female heirs and proposes this as the 'illah. As she shows, in all cases where the male heir has an obligation to support the female heir, the male heir receives a double share. In cases where the male heir does not have an obligation to support the female heir, the male heir does not receive a double share. The point of all of this is, Chaudhry is not just making these claims to defend Islam based on her wishes or desires nor is she making up some innovated or unsupported argument. Instead, she is using the methodology of Islamic jurisprudence itself to prove her case. People might be able to ignore the two articles I linked earlier in this entry as fanciful and say "oh, sure, liberal Western Muslims say that but traditional Muslims never heard of it". They can't brush off Chaudhry's article so easily. As a footnote to this, until 1971 the state of Idaho had a law regarding intestate succession that stated that in the case of competing petitions from otherwise qualified individuals of the same priority relationship, 'males must be preferred to females'. This law was overturned by the Supreme Court in Reed v. Reed, 404 U.S. 71 (1971). If even the "enlightened West" still had these laws as recently as 32 years ago, maybe we ought to cut developing Muslim countries a bit more slack, hmm?