Twenty-second Amendment to the United States Constitution
As worded, the primary focus of the 22nd Amendment is on limiting individuals twice elected to the presidency from being elected again. Due to this, several issues could be raised regarding the amendment's meaning and application, especially in relation to the 12th Amendment, ratified in 1804, which states, "But no person constitutionally ineligible to the office of President shall be eligible to that of Vice-President of the United States". While it is clear that under the 12th Amendment the original constitutional qualifications of age, citizenship, and residency apply to both the president and vice president, it is unclear whether someone who is ineligible to be elected president could be elected vice president. Because of this apparent ambiguity, there may be a loophole in the 22nd Amendment whereby a two-term former-president could be elected vice president and then succeed to the presidency as a result of the incumbent's death, resignation, or removal from office (or even succeed to the presidency from some other stated office in the presidential line of succession).
Thirteenth Amendment to the United States Constitution
While the Constitution does not provide the President any formal role in the amendment process, the joint resolution was sent to Lincoln for his signature. Under the usual signatures of the Speaker of the House and the President of the Senate, President Lincoln wrote the word "Approved" and added his signature to the joint resolution on February 1, 1865. On February 7, Congress passed a resolution affirming that the Presidential signature was unnecessary. The Thirteenth Amendment is the only ratified amendment signed by a President, although James Buchanan had signed the Corwin Amendment that the 36th Congress had adopted and sent to the states in March 1861.