I'll be traveling to the UK (London) on a study abroad in the spring and will be bring my laptop for school and intern purposes. I was just curious what/if any rights UK customs has to search laptops at the border, and how common laptop seizure and search is when returning to the good old U.S.A.
From the US Customs and Border patrol website:
As Secretary Chertoff noted in a recent op-ed, "Of the approximately 400 million travelers who entered the country last year, only a tiny percentage were referred to secondary baggage inspection…[and] of those, only a fraction had electronic devices that may have been checked."
So, (if they are being truthful), having your laptop seized and searched is not at all common. I think it is very unlikely unless you either gave them some cause for suspicion, or if they were already tracking you before you entered the US (i.e. you were already on some kind of watchlist).
The UK can indeed take your laptop and search it (like any other country can), and can have you prosecuted if you fail to decrypt your encrypted files for them.
All countries demand the right to search possessions brought into the county, including electronic devices. Where encrypted storage devices are concerned many countries can also demand the owner provide customs with any necessary decryption keys.
The Regulation of Investigatory Powers Act 2000 (RIPA), Part III, activated by ministerial order in October 2007, requires persons to supply decrypted information and/or keys to government representatives. Failure to disclose carries a maximum penalty of two years in jail.
The Fifth Amendment to the United States Constitution protects witnesses from being forced to incriminate themselves, and there is currently no law regarding key disclosure in the United States.
However, the article goes on to list many cases in the US where defendants have been forced to surrender decryption keys regardless of this lack of legislation.
In practise though, as others in this thread have attested, these issues are very rarely a problem; the vast majority of laptops are never searched. Plus, if one did need to securely move sensitive data into a country it would be trivial to download it though an encrypted channel after arrival.
I would say I've carried a laptop into the US at least 20 times in the last ~15 years. Never once has any customs official so much as laid eyes on the machine, let alone looked at what's on it.
However, I've never been coming in from a sex tourism country and I've always been with my wife at the time. My understanding is that if I were returning alone from places like Thailand that it might draw more scrutiny.