In E and G space ultralights can pretty much do as they please. D space and higher they need permision from the controlling athority, ie tower. They're not allowed in A space except below 1,000ft AGL (That's how Mike Jacober of Anchorage was able to fly his over McKinley). And they're not allowed above congested areas at all. In Fairbanks the tower has defined a corridor below 1,000ft AGL into Metro Field that the ultralights are allowed to use, but only if they've gotten certain training from a CFI on airspace rules and visited the tower, or have a pilots certificate, unless they've changed the rules in last 5 years.
Phil