The Obama administration's decision requiring church-affiliated employers to cover birth control was bound to cause an uproar among Roman Catholics and members of other faiths, no matter their beliefs on contraception.

The regulation, finalized a week ago, raises a complex and sensitive legal question: Which institutions qualify as religious and can be exempt from the mandate?

For a church, mosque or synagogue, the answer is mostly straightforward. But for the massive network of religious-run social service agencies there is no simple solution. Federal law lays out several criteria for the government to determine which are religious. But in the case of the contraception mandate, critics say Health and Human Services Secretary Kathleen Sebelius chose the narrowest ones. Religious groups that oppose the regulation say it forces people of faith to choose between upholding church doctrine and serving the broader society.

"It's not about preventing women from buying anything themselves, but telling the church what it has to buy, and the potential for that to go further," said Sister Carol Keehan, president of the Catholic Health Association, representing some 600 hospitals.