BOSTON — The Boston Archdiocese’s Catholic Charities said Friday it would stop providing adoption services because state law requires them to consider gays and lesbians as parents. The social services arm of the Roman Catholic archdiocese has provided adoption services for about a century. But it says state law allowing gays to adopt runs counter to church teachers on homosexuality. “The world was very different when Charities began this ministry at the threshold of the twentieth-century,” the Rev. J. Bryan Hehir and trustees chairman Jeffrey Kaneb said in a joint statement. “The world changed often and we adapted the ministry to meet changing times and needs. At all times we sought to place the welfare of children at the heart of our work. “But now, we have encountered a dilemma we cannot resolve,” they said. The state’s four Catholic bishops said earlier this month that the law threatens the church’s religious freedom by forcing it to do something it considers immoral. Eight members of Catholic Charities board later stepped down in protest of the bishops’ stance. The 42-member board had voted unanimously in December to continue considering gay households for adoptions.