Why Guaidó is the President of Venezuela

Diego Zambrano writes at Lawfare:

The U.S., along with dozens of other states, recently recognized Juan Guaidó, the president of Venezuela’s National Assembly, as the legitimate president of Venezuela. Discussion of international recognition of Guaidó’s presidency has focused largely on the political implications of the move as a rejection of Nicolás Maduro’s corrupt dictatorship. While recognition typically focuses on a ruler’s de facto control over a territory, Guaidó’s de jure status under the Venezuelan Constitution is also crucial. If Guaidó is clearly president under Venezuelan law, then recognition seems warranted here. Even setting aside the fact that Maduro’s kleptocratic rule has caused a humanitarian catastrophe, I believe that the best and most sensible reading of the Venezuelan Constitution leads to the conclusion that Juan Guaidó is now the interim president of Venezuela.

What is the argument for this:

In 2018, the unconstitutional assembly called for, and organized, a presidential election—in direct violation of the constitution. The alternate assembly sidelined the actual National Assembly’s role, staffed the National Electoral Council with Maduro loyalists, and ensured another “election” that would keep Maduro in power.
All of that unconstitutional procedure means that the so-called presidential election of 2018 was de jure null and void.

And what does that mean:

Because of these violations, and others, there simply was no election under any reading of the Venezuelan Constitution. The National Assembly declared that the process did not constitute an election; the international community overwhelmingly rejected it as a sham; and opposition Venezuelan political parties boycotted the process. The U.N. human rights chief noted that the 2018 process did not “in any way fulfill minimal conditions for free and credible elections.”
The key to understanding Guaidó and the National Assembly’s argument is that, when Maduro’s presidential term concluded on Jan. 10, there was no elected president to assume the presidency. Maduro’s claims to the contrary are irrelevant, null and void.
In a situation with no president, Article 233 of the constitution regulates the presidential line of succession. In this case, that article is best read to mean that the president of the National Assembly should temporarily assume the presidency.

So Maduro’s term expired on 10 January, and hence Guaido becomes interim President. The exact clause is:

[W]hen an elected President becomes permanently unavailable to serve prior to his inauguration, a new election by universal suffrage and direct ballot shall be held within 30 consecutive days. Pending election and inauguration of the new President, the President of the National Assembly shall take charge of the Presidency of the Republic. 

This is why almost every Western country in the world, except New Zealand has recognised Guaido as the interim President.