The federal Freedom of Information Act, which assures access to nearly all government and court records, became law 40 years ago. That’s worth celebrating, say public interest groups, authors, historians, librarians, lawyers, journalists and other advocates for open government.

The anniversary is being marked this week around the country with “Sunshine Week” conferences, ceremonies, podcasts and public service ads. It’s called Sunshine Week because the Freedom of Information law, known as FOI for short, put government documents and actions out in the “sunshine” – open to the bright light of public attention.

Admirers of the law say now is a particularly important time to appreciate the access that Congress and President Lyndon B. Johnson guaranteed in 1966. They feel some officials use the Iraq war, anti-terrorism efforts and other developments to justify improper secrecy.

Law’s uses: It was applied to obtain the records of military tribunals handling cases against Afghan detainees at the U.S. base in Cuba. It’s currently cited in a federal lawsuit against the Secret Service to obtain White House visitor logs that show how often lobbyist Jack Abramoff was at the White House.

Backers say: Conducting local, state or national government and court business in the shadows beyond public view allows misbehavior, citizen distrust and bad results. Bids, contracts, spending, policy decisions, records of meetings and virtually all other government business should be open to the taxpayers financing it.

Challenges: The current Justice Department has a confirmed policy of resisting FOI requests when possible by claiming exemptions from the law. National security concerns increasingly are cited as reasons for withholding “sensitive” information. The CIA this year removed more than 55,000 pages of previously declassified historical records from the National Archives and reclassified the information. E-mail records are not always archived and available for access under the law, as agencies have inconsistent policies on what is saved and for how long.