The World Trade Organization (WTO) is the multilateral negotiation housed by the Most Favoured Nation and National Treatment in fairness accounts. However, the WTO encourages forming bilateralism of the Preferential Trade Agreement (PTA), or Free Trade Area (FTA) in the GATT Article 24. Bilateralism within multilateralism is incompatible. The book finds what the genesis of the PTA; if it is the special law (lex specialis) to the WTO law or the post law (lex posterior) after the WTO. The view of lex specialis has more room to be compatible with the WTO. The view of lex posterior increases the autonomy of the Members to gain the bilateral benefits. In the WTO, the Committee of the Regional Trade Agreements (CRTA) monitors the PTAs but inactive. In the context of the GATT article 24, there is the interpretive hole on the interpretation of the "substantially all the trade;" which is opened for ambiguous decisions. Is it overcome by the view of the lex specialis, or lex posterior, or the stronger CRTA? Last, gravity equation takes the distance and the GDP as the determinants of the valuable trade; the best pair of the PTAs is the US and Canada, the second is Switzerland and the EU.