Here is an article that says the TSA can not only search your laptop but they can also copy any files they want and give them to third-party agencies:

Domestic travelers have become familiar with intrusions and searches at Transportation Security Administration security checkpoints. But as the ACLU has recently discovered, international travelers are not only having their laptops seized and searched by Customs and Border Protection, but agents are making copies of files and giving them to third-party agencies. The ACLU filed a Freedom of Information Act lawsuit against the government, which turned over hundreds of pages of documents revealing startling information about how much access—and how little oversight—agents have to your gaming laptops when you travel.

For instance, over a period of nine months, CBP agents searched over 1,500 devices, including laptops, thumb drives, cell phones, and DVDs. Last year, agents transferred 282 files from these devices to third-parties. Under current policy, CBP is not required to justify the searches. Interestingly, of those files, only four were justified under "national security" concerns, and apparently encrypted files were sent to unknown agencies for "translation/decryption".