The issue of standing in the Supreme Court's same-sex marriage cases.

Linda Greenhouse explains the 2 standing problems in a way that is accessible to the general reader.

The Windsor case is especially striking, because the plaintiff's stake in the case is knock-you-over-the-head clear and tangible:

Ms. Windsor owes more than $300,000 in federal estate tax on the property left to her by the woman to whom she was legally married in the eyes of New York State. Had she been married to a man, she would have inherited the property tax-free. With DOMA barring the federal government from recognizing same-sex marriage, and the Obama administration taking the position that it will enforce the law until the Supreme Court or Congress tell it otherwise, there certainly seems to be a controversy between the parties sufficient to meet the test of Article III jurisdiction.

But the Obama administration declines to defend the constitutionality of DOMA, and Windsor won in the lower courts, making things nonadversarial, and the federal courts can only resolve actual controversies between the parties. But it's not as if DOMA has gone away. It still affects people, and Congress isn't about to repeal it.

Democrats in Congress wanted no part of defending DOMA, even though the statute had passed both houses in 1996 by big bipartisan majorities and was signed into law by President Bill Clinton. So a five-member House leadership body called the Bipartisan Legal Advisory Group decided, over the objections of its two Democratic members, to take over the executive branch’s abandoned defense of DOMA....

The question in the case is whether this Bipartisan Legal Advisory Group can take over defending the law and thereby preserve the adversarial quality of the case. Obviously, it will be litigated with intensity and excellence. The Group has Paul Clement as its lawyer. But that's not the point in standing doctrine.