International Standards For Phytosanitary Measures No. 15 (ISPM 15) were developed by the International Plant Protection Convention (IPPC) and addresses the need to treat wood materials, used to ship products between countries. Its main purpose is to prevent the international transport and spread of disease and insects that could negatively affect plants or ecosystems.
ISPM 15, 2009 (in English) can be found here:
More information about the ISPM 15 and countries that have adopted ISPM 15 can be found at http://en.wikipedia.org/wiki/ISPM_15
MAISTORM sources pallets that are heat treated according to ISPM 15 from certified and reliable suppliers, so you do not have to worry about the legitimacy of the HT claim on the pallet!