Removes the block on a unit placed by the “block unit” command.

unblock unit (name of unit)

in (integer, create a scheduled event to unblock this unit in this many seconds)
at (date, like the in parameter, an applescript date when you wish the unit to be unblocked)

for (integer, create a scheduled event to reblock this unit in this many seconds)
until (date, like the for parameter, an applescript date to create an event to reblock this unit at a specific date/time)

unblock unit "Outside Siren"