Should the policies of a school or business require a person to get explicit permission for sexual activity from the prospective partner?

Pro: Getting explicit permission for sexual activity from the prospective partner insures that no one has to endure unwanted advances.

Pro: The person who has received explicit permission for every sexual act performed with another can be reassured that no honest charge of rape can be made.

Con: Very often the letter of a law can be obeyed while the spirit of that law is violated with impunity. This makes certain policies ineffective, if not completely inadvisable. For example, a person might ask questions ostensibly to determine the permissibility of sexual activity, all the while intending only to aggravate the one to whom the questions are directed. Examples of such questions are "Would you like to take a shower together?" or "Would you like to go to bed with me?" In certain circumstances, say with complete strangers, or with persons known to be shy, such 'requests for permission' could be inappropriate. And yet, given a policy that requires individuals to get explicit permission for every sexual advance, one could argue that such offensive questions were necessary.