When a C-corp is formed, a set of by-laws should also have been drawn up to go along with the articles of incorporation.   The by-laws define the powers of the different officers and directors.   As such, the ability of the president to override the decision of the secretary/treasurer would depend on the extent of his rights and duties established in the by-laws.  If you are not sure what your by-laws are, have a corporate or business attorney go over all of the company's articles of incorporation-- they should be able to quickly separate each of the documents and explain the extent of the power authorized.