Well, not quite. Anyone can request a Whie House tour through their Congressional Rep or Senator, these tours are self-guided and take place 5 days a week with timed entry.Although they are obviously canceled if something is taking place in the function rooms that are part of the tour and can be canceled at any time for any reason, really.

There are special "VIP" tours that are also given. The tours for the general public take place regardless of whether the First Family is away or not. Overseas visitors often have problems getting tours as they obviously don't have a representative in Washington. As the White House web site says, "contact your embassy". Problem being many of the embassies are simply too busy to deal with these requests and thus provide no help to their citizens requesting them.