Unfortunately, all of the Dr. Jackson’s articles have been removed from the Washington Post website including the one about same-sex marriage rights. But you can still read his words at The Politcal Muslim: Dr. Jackson in an article in the Washington Post:
A major feature of this framework is the tendency to assume that religion, and therefore Islam, invariably aims to translate its every moral sensibility into laws and policies. On this understanding, if we know a religion’s moral judgments, we can assume that we know its legal/political ones.
This understanding, however, is not consistent with the perspective of Traditional – to be distinguished in many ways from Modern – Islam. Simply put, before its encounter with the vision of the modern nation state, Islam was pluralistic: neither law nor politics, i.e., the applied legal order, was a zero-sum game.
One Islamic school held a substance to be unlawful; another held it to be harmless; neither, however, could bind the other to its view. Muslims unanimously condemned pork and wine consumption as immoral; but they did not deny this to Christians or others whose religious values allowed it.
In short, Islam did not seek to translate its every moral value or sensibility into a political order consisting of rules to be imposed on the entire society.
In this light, I have serious misgivings about a constitutional amendment that would ban gay unions across the board, not because I support or even condone homosexuality but because I believe that marriage is essentially a religious institution whose definition should be left to religious communities.
The state should be limited to the role of executor, just as it does in the case of the bylaws of professional organizations or the terms of multinational contracts.
In other words, if a religious community (e.g., the Episcopalians) deems gay unions to be consistent with Christianity, the state should only act to curtail their religious freedom for a compelling state or public interest. Otherwise, the political value of religious freedom should trump the moral perspective of the state. The matter, in other words, is not one of morality but one of religious freedom in a pluralistic society.