Lee,
It is covered under the RA 8533 (Otherwise known as the Family Code of the Philippines) Chapter !, para 26, as amended.
I remember the RA, and the EOs governing this, were amended in 2010 or thereabouts.
Basically, a foreigner who instigates the divorce, outside the Philippines obviously, is free to remarry, as is the Filipino/a spouse.
If the Filipino/a instigates the divorce, the foreigner is OK to remarry, but the Filipino/a is not.
Fair? No it's not, but maybe change is on the way.
Peter