The International Society of Professional Wedding Photographers (ISPWP) is a rarity among wedding photography organizations. Photographers cannot simply buy an ISPWP membership, they have to earn it.
Their requirements are experience, talent, and professionalism. To be accepted, a photographer must have shot at least 50 weddings, submit their portfolio for review, agree to operate under the ISPWP Code of Conduct, and have an ISPWP Sponsor or four references. And THEN they have to be voted in by current members.
In short, when you hire an ISPWP Photographer, you are hiring a talented veteran with a track record, peer recognition, and a passion for creating heirloom images of your wedding.