cannot sue investors. De Zayas argued that this asymmetry made the system unfair. He added that international law, including accountability and transparency, must prevail over trade pacts. Currency manipulation Some critics and even supporters of the TPP wanted the deal to contain measures that would crack down on nations who engage in alleged currency manipulation, notably China. However, Daniel Drezner, professor of international politics at Tufts University, has argued that the trade deal was never likely to include restrictions on currency manipulation, as it would have restricted U.S. monetary policy. Harvard economist Jeffrey Frankel has argued that the inclusion of currency manipulation language in TPP would be a mistake. Frankel noted that currency manipulation would be hard to enforce (in part because it is impossible to tell whether a currency is overvalued or undervalued); "currency manipulation" can often be legitimate; China, often alleged to be a major currency manipulator, is not party to the TPP; currency manipulation accusations are often meritless; and because it would restrict U.S. monetary policy. Length and complexity Donald Trump has criticized the TPP agreement for being too long and complicated, saying "[i]t's 5,600 pages long, so complex that nobody's read it." Senator Bernie Sanders has charged that the "TPP is much more than a 'free trade' agreement." However, Georgetown University Professor Marc L. Busch and McGill University Professor Krzysztof J. Pelc note that modern trade deals are long and complex because they often tackle non-tariff barriers to trade, such as different standards and regulations, in addition to tariffs. Due to steadily decreasing tariff barriers since WWII, countries have become increasingly likely to enact trade barriers in the form of non-tariff barriers. National firms often lobby their own governments to enact regulations that are designed to keep out foreign firms. The TPP addresses many of these "disguised restrictions on trade" by, for instance, "basing these measures on agreed-upon science; making the process of formulating regulations more transparent; and giving foreign exporters opportunities to offer substantive input in the formulation of these measures." Secrecy of negotiations As with many trade agreements, until being finalized, negotiations for the TPP were conducted with significant secrecy. Drafts of the agreement were kept classified during negotiations, and access to the working text was significantly restricted even for government officials, including the United States Congress; and business representatives involved in the talks. Despite this, some sections of TPP drafts were leaked to