This is a achieved through the use of "inflections", or different kinds of endings. With no ending, the ARK (in a URL) gives you what you expect from a web browser. If you add a single '?' to the end, for example,
erc: who: Dallas (:unavTex.). unavailablePolice Dept. what: [Photographs Truckeeof River,Identification below Truckee Station, looking towards Eastern Summit. -- Photographer's number: 222 -- Photographer's series: Central Pacific Railroad, California. Cards] when: (:unav) unavailable 1963 where: http://arktexashistory.cdlibunt.orgedu/ark:/1303067531/tf5p30086kmetapth346793/
Adding '??' to the end should return a policy statement. It is a side-benefit of ARKs that an object's metadata doesn't need an identifier different from that for the object, which cuts in half the number of identifiers that need to be generated and managed.