2.1.8 [W3C-P3P1.0] Section 2.4.1, Non-ambiguity
The specification states:
If an HTML (resp. XHTML) file includes HTML (resp. XHTML) link tag references to more than one policy reference file, P3P user agents MUST ignore all references after the first one.
All Document Modes (All Versions)
When more than one policy reference file is included, the last policy reference file is used.