As Archbishop of Boston, he led the third-largest Roman Catholic community in America, and traditionally one of the most important.
He was the most senior prelate in the country, having become archbishop in 1984 and a cardinal the following year, and was considered a close ally of the Pope.
But following deeply damaging revelations about abuse of children by clergy, a group of 58 priests called for his resignation in December.
It was a shocking declaration from the clergymen - who under church law had sworn to obey him - and echoes reverberated as far as Rome.
Influential
As Archbishop of Boston, Cardinal Law was a high-profile figure both in Church matters and in the wider world.
He spoke out in favour of affordable housing and against anti-Semitism.
He raised millions of dollars to help victims of disasters including Hurricane Mitch, and worked to improve ties between Catholics and other Christian groups.
But he also took deeply traditional positions on such matters as Aids, abortion, same-sex marriages, and education policy.
He banned advocates of women's ordination from meeting on Church property and urged Catholics to vote against the Democratic White House candidates in 1984, Walter Mondale-Geraldine Ferraro, because of Mrs Ferraro's support for abortion.
Hard to pigeon-hole
The author of the book Boston Catholics, Thomas O'Connor, tells a story to illustrate the complexity of Boston's former archbishop.
"When I asked people to describe Cardinal Law in a word or two, I never - not once - got an answer," he told the Boston Globe.
"And why? Because it's so hard to pigeon-hole him. I don't mean this in a negative way, but he's a very subtle, very enigmatic character with many dimensions to his personality."
Bernard Law
1931: Born in Torreon, Mexico
1961: Ordained a priest
1973: Appointed bishop
1984: Became Archbishop of Boston
1985: Appointed cardinal
2002: Vatican accepts his resignation
Cardinal Law was born in Torreon, Mexico, the son of a US army colonel, 1931.
He was ordained in 1961 and became heavily involved in civil rights work in Mississippi. His name was included on a hit list compiled by segregationists.
He was promoted to become bishop of Springfield Cape Girardeau in Missouri in 1973.
There, he fostered links with other denominations, welcomed refugee priests from Vietnam and set up local social welfare projects.
Boston
Eleven years later he was appointed Archbishop of Boston.
A year later he rose to the position of cardinal, and established himself as a major figure in a city where Catholics enjoy pre-eminence in the fields of politics and business.
Until recently he enjoyed the support of the region's black, Latino and other minority communities.
As the sex abuse scandal enveloped the US Catholic Church in the spring, he gave an insight into his feelings when he told the Los Angeles Times: "I personally have in the past weeks experienced closeness to Jesus on the cross that I have never before in my life."