Fire Commissioner Lloyd Ayers resisted the mayor's order, based on the little-known Flag Code, which says that only the president can order an American flag to be lowered.

Nutter said yesterday that he was simply asking that city flags be flown at half-staff - which the Fire Department is doing.

But just what is the Flag Code, anyway?

It is Section 1 of Title 4 of the United States Code - a federal law, but with no penalty for failure to comply.

It states, in part: "By order of the President, the flag shall be flown at half-staff upon the death of principal figures of the United States Government and the Governor of a State, territory, or possession, as a mark of respect to their memory . . . In the event of the death of a present or former official of the government of any State, territory, or possession of the United States, the Governor of that State, territory, or possession may proclaim that the National flag shall be flown at half-staff."

It says that the U.S. flag shall be flown at half-staff for 30 days after the death of a president or former president, and for 10 days after the deaths of several other federal officials.

The code lists days on which the flag can be flown at half-staff, including New Year's Day, Inauguration Day (Jan. 20), Lincoln's birthday, Washington's birthday, Easter, Mother's Day, Armed Forces Day, Memorial Day (half-staff until noon), Flag Day, Independence Day, Labor Day, Constitution Day, Columbus Day, Navy Day, Veterans Day, Thanksgiving and Christmas.