JR:

The 2006 International Residence Code (IRC) which is currently in use in Honolulu requires smoke alarms in Section R313 in new homes and in additions which add bedrooms.

The 2006 International Building Code (IBC) which is currently in use in Honolulu for larger buildings and townhouses requires smoke alarms in Section 907.2.8.

Existing buildings have always been exempt from mandatory upgrades to the current code.  Otherwise construction work would be continuous.  However, if you want a permit to do something to your existing house, (depending upon the planned work) you may be legally forced to upgrade.